How to understand the Xcode?

Through my whole life using computers generally, I have figured out that any software could be well understood by practice, but actually the case here seems much different.
My question is not regarding the interface, structure of the project...etc, I would like to understand the coding itself, where and when every code to be used and how it works, there are lots of codes those can be used in different cases, It is not possible that one person can understand every single tip of the Xcode or any other programming language, but I want to know at least which way should I take (courses, books, tutorial....), I want something that gives the general idea and concept of the things.
I am developing a game now, succeeded in creating some different pages of the game where it take you to the setting, high score...etc with some simple graphics, linked them together using the available options, but to make the game work it needs pages of coding, looking for sample codes is also not practical in my opinion.
I believe that understanding the top used 100 code in my opinion will be sufficient for a beginner.
Thanks

Xcode is the IDE.
Objective-C is the language typically used.
There's lots of getting started stuff at https://developer.apple.com

Similar Messages

How to understand the STAD relevant for RFC

Hello performance experts.
I have question about how to understand the STAD relevant for RFC.
I want to know how to calculate the response time of action of "Push save buttion"
which call function module by RFC.
In our system, the screen is created using web dynpro and after push the button,
function module for application will be called.
When I push Save button, 2 STAD line is created.
One is for function code " SAVE" and the other is for "RFC".
Line for "SAVE" include RFC as client, and RFC line has RFC info as server (also client)
I wonder how I should calculate the response time of action"Save" button in following case.
Should I add the 2 response time?
1) 5,867 ms +   5,797 m is collect?
2) 5,867 ms include RFC time, so no need to sum the value and 5,867 ms is collect??
3) 590 ms +   5,797 ms is collect?
4) Or other calculation is correct ?
1) STAD for function code:
CPU time                     578 ms
RFC+CPIC time              5,280 ms
Total time in workprocs      594 ms
Response time            5,867 ms
Processing time              590 ms
Load time                      1 ms
Wait            5,273 ms
Roll (in+wait) time        5,274 ms
as Client
Number    Connections                              1
           Destinations                             1
           Users                                    1
           Calls                                    2
Time      Calling                              5,280   ms
           Remote execution                    10,527   ms
           Idle                                11,110   ms
Data      Sent                               135,836   Bytes
           Received                               620   Bytes
2) STAD for RFC
CPU time                   1,406 ms
RFC+CPIC time                  9 ms
Total time in workprocs    5,080 ms
Response time            5,797 ms
Processing time            2,132 ms
Load time                     50 ms
Roll (in+wait) time          718 ms
Database request time      2,882 ms
Enqueue time                  16 ms
Roll time
Wait              717 ms
as Client
Number    Connections                              1
                  Destinations                             1
                     Users                                    1
                       Calls                                    4
Time      Calling                                  9   ms
          Remote execution                         1   ms
          Idle                                     0   ms
Data      Sent                                   686   Bytes
             Received                             1,360   Bytes
as Server
Number    Connections                              1
          Destinations                             1
          Users                                    1
          Calls                                    2
Time      Calling                              5,272   ms
          Remote execution                     5,269   ms
          Idle                                        11,118   ms
Data      Sent                                   620   Bytes
          Received                           135,760   Bytes
Thanks for your cooperation in advance.
Keiichiro

Hi Keiichiro,
I wonder how I should calculate the response time of action"Save" button in following case.
Should I add the 2 response time?
1) 5,867 ms +   5,797 m is collect?
2) 5,867 ms include RFC time, so no need to sum the value and 5,867 ms is collect??
3) 590 ms +   5,797 ms is collect?
4) Or other calculation is correct ?
It depends of what you mean with response time of action "Save" button.
If you mean ALL time, the value is 5.867 because the local time from save was 594ms, the "external" RFC time was 5280ms.
If you want separete analysis, the 594ms is your option since the 5280ms is in other part...
Also, analysing the other part there's another other part which represents a good part of processing time:
Database request time      2,882 ms
Hope this help youl.
Regards, Fernando Da Ró

[q] how to understand the 'order' of a list?

hi,everyone
there's a test program:
import java.util.*;
public class testList
void test()
LinkedList ll= new LinkedList();
ll.add("3");
ll.add("1");
ll.add("2");
ll.add("5");
ListIterator li = ll.listIterator();
while (li.hasNext())
System.out.println(li.next());
public static void main(String[] args)
testList tl = new testList();
tl.test();
As we know, order is the most important feature of a List.
But this program's result is " 3 1 2 5 " which is not a sorted list!
How we understand the phrase 'order' ?
And , is there any method in Collection which can sort the elements in one collection (list or set)?
thanx a lot!

As we know, order is the most important feature of a
List. Yes, and it preserves the order you have used to put elements in the List. :)
But this program's result is " 3 1 2 5 " which is not
a sorted list!Well, what order to you actually like? "1 2 3 5"? Why not "5 3 2 1"? And for more complicated objects "natural" order may be even less obvious. And never forget that List may contain objects that belong to different classes - for example Integer, String and Date - how they are to be ordered? (Of course, such usage is not recommended).
How we understand the phrase 'order' ?
And , is there any method in Collection which can
sort the elements in one collection (list or set)?There are sort-methods in java.util.Collections class.

How to understand the hierarchy structure of 0PLANT io?

how to understand the hierarchy structure of 0PLANT io ?
i can understand the hierarchy structure of PRODUCT io,
well, i hope someone could explain the hierarchy structure of 0PLANT io
thanks.

Hi
You can use following hierarchy tables
RSTHIERNODE - Texts of Non-Postable Hierarchy Nodes
RSEHIERNODE - Master Data: Hierarchy Nodes that Cannot Be Posted To
RSMHIERNODE - Master data: Hierarchy nodes that cannot be posted to
RSHIEDIR - Hierarchy Catalog
RSHIEDIRT - Hierarchy directory texts
RSREQHIER - Data Request hierarchy
RSROLEHIERARCHY - Role hierarchy
In addition to these have a look at K table & I table for 0PLANT.
K table - Hierarchy SID table
I table - Hierarchy structure table
Hope this will help..!!
Thanks,
Vikrant

How to understand the way OBIEE implements outer joins?

Hello guys
I have a few scenarios where I have to implement outer joins and inner joins between dimensions and facts..
There are 2 ways as far as I know that allows me to implement outer joins in BMM layer.
1, Join the Logical dim table A to Logical Fact table B using outer join. The modeling will look like the below:
A Dim ---outer------B fact -----------inner----C Dim
By this design, the query that selects columns from all 3 tables will look at this:
select columns from ((B fact inner joins C on key1 = key2) left outer joins on A dim) on key3=key4)..
2, Join logical dim table A to fact table B inside the LTS of fact B by mapping the LTS B to dim A using outer join. then join fact B to C:
B fact (mapped to fact B outer join Dim A) ------------inner -------C dim
By this design, the query that selects columns from all 3 tables will look at this instead:
select columns from C, B left outer join A on key1=key2 where key3=key4
Comparing these 2 queries, the first one seems to do inner joins first and then outer join the result set to Dim A, the second query seems to outer join Dim A first and the result set inner joins to Dim C..
I ran the same report using these 2 different designs, and the data comes out very different. The report of the first query is much smaller than the report of the second query...
Can anyone help me understand how OBIEE understands outer joins? The second query is so far giving the right result, however, I can't get rid of the outer join in the query even if not selecting columns from Dim A, which is impacting the performance of other reports without Dim A.
Your inputs will be greatly appreciated
Thanks
Edited by: user7276913 on Apr 20, 2010 9:31 AM
Edited by: user7276913 on Apr 20, 2010 9:31 AM

Xcode is the IDE.
Objective-C is the language typically used.
There's lots of getting started stuff at https://developer.apple.com

How to understand the Error message of the connection of OPC server

hi guys, one issue need your help
when I run the NI OPC servers, one error message will appear in the process information.
Just like as followed:
===========================================================================
2011-6-23   11:50:05   Default User   NI OPC Servers   Stopping Simulator device driver.
2011-6-23   11:50:05   Default User   NI OPC Servers   Closing project D:\National Instruments\Shared\NI OPC Servers\projects\simdemo.opf
2011-6-23   11:50:25   Default User   NI OPC Servers   NI OPC Servers
2011-6-23   11:50:25   Default User   NI OPC Servers   Unable to load driver DLL 'D:\National Instruments\Shared\NI OPC Servers\drivers\dataforth_isolynx_u.dll'
more messages
=============================================================================
how to understand "2011-6-23   11:50:25   Default User   NI OPC Servers   Unable to load driver DLL 'D:\National Instruments\Shared\NI OPC Servers\drivers\dataforth_isolynx_u.dll'??????
Thanks

Hi!
I have the same problem when opening the OPC Server.
Unfortunately I have no solution, but I think it has something to do with incorrect Certificates and is more of a Windows Problem.
If anybody can help, please let us know!
Best Regards
Martin

How to understand the storage systems?

How to get more and more or complete understanding of the storage systems like understanding the hardware components involved,best configuration for the hardware,best practices.
Is there any book for the storage knowledge for DBA's.

LearningOracle,
I shall second to Sybrand's suggestion for the Scaling Oracle 8i book. That's an awesome book , covering alot of stuff , for both oracle and operating systems. Its available for download from here,
http://www.scaleabilities.co.uk/book/scalingOracle8i.pdf
In addition to this, I would say that you start reading the books/notes which are there for SAN and other systems. There is no dedicated book for storage systems for DBAs AFAIK or I should say ,there is none which is very popular. If you are interested in managing the operating system for ORacle prospective, OU offers a course for System Admins for managing oracle on linux, that ha coverage for storage as well. That should be helpful,
http://education.oracle.com/pls/web_prod-plq-dad/show_desc.redirect?dc=D46592GC10&p_org_id=1001&lang=US
HTH
Aman....

How to understand the sessionManager(JMF)

I am struglling for a online conference project ,C/S structure,using JMF and RTP ,but i failed to understand the sessionmanager ,what is a sessionmanager ? how to use it ? help!
Edited by: orientsoar on Mar 27, 2009 6:59 AM

orientsoar wrote:
I am struglling for a online conference project ,C/S structure,using JMF and RTP ,but i failed to understand the sessionmanager ,what is a sessionmanager ? how to use it ? help!SessionManager is actually depriciated, you should be using an RTPManager instead.
To learn about using RTP and JMF, I'd recommend the following resource...
[http://www.cs.odu.edu/~cs778/spring04/lectures/jmfsolutions/examplesindex.html]

Suggestions requested on how to understand the JVM

Hi
I would like to understand the fundamentals of the internals of the Java language and I have made a guess that the JVM is probably a good place to do that. I would like to know how to proceed. I would like to be able to write code for the JVM, understand classloaders, garbage collection, etc.
thanks
ilango

Refer Sun's JVM specification. To understand either Sun or IBM's java garbage collection...simply google it.

How to understand the "New Item" icon at the bottom of the Project window

I'm trying to understand that small "New Item" box at the bottom of the project window better. I'm aware that when I bring video clips into my project, if I drag them to this box, PPCS5 will add them to the timeline. I partially understand the positive reasons for doing so, primarily that PPCS5 will correctly identify the type of video being brought into the project. I know that if I select all my clips and drag them to the new item box, that all my clips will be added to the timeline at the same time and all together on the timeline. There are many things I don't understand about it. If I add my clips one by one using the "New Item" icon, they will show up as separate sequences on the timeline. If you try to add another clip at a later time, can that clip not be added using the "New Item" box? One other question is what would be the advantage in putting clips on the timeline as separate sequences? And one further question is do you drag other items to this box besides video clips? Like music, and still images?

Dragging something to the New Item icon doesn't just add that something to a sequence. It actually creates the correct sequence for the something to be added to.
You do this once, when you need a new sequence. Anything else you want to add to that sequence you do by other means.

How to understand the strange parameter values shown by 'pstack core'

I encounterred a problem that led to a core dump. I use 'pstack core' to shown the calling stack.
However I could hardly understand some of the parameter values below:
core 'core.150108' of 5016: cmcfun
ff1e1370 __1cLComEndPointFsendv6MpnFiovec_i_i_ (c, ffbfedf8, 2, 2, c, 0) + 4
Why did the 'this' pointer of the instance of class ComEndPoint become 0xc? I don't think it is a valid value of pointer. Does anybody have any idea about this problem?
ff1e5b00 __1cYComTransaction_Icallback6FpnPpdo_transaction_pcii_v_ (6ab90, 0, 0, 0, ffbff1b8, 0) + dc
According to the source code, the 3rd parameter in the function below, which value is 0x66, was not changed in the scope of the function. However it became 0x0 when it was used as the 4th parameter to call the function above. What't the matter?
ff1528e8 pdo_dispatch (6ab90, ad, 66, 0, 0, 0) + dc
I heard that Sun C++ uses 'register windows' to pass the parameters, i0~i5 are used for the first 6 ones. Somebody told me that what I saw in the pstack might not be creditable because the registers might be changed within the function. Is that so? Would anybody plz tell me more details?
Thanks in advance.
Edited by: DirtyBear on Feb 15, 2008 1:17 AM

Register windows are a property of the SPARC computer architecture, not a property of a compiler. SPARC has multiple sets of registers. The function call instruction advances the "register window" to reveal the next set of registers, if there is one. If not, the registers are spilled to the stack to free up a window. The function return instruction moves the window back. (It's a purely hardware feature.) Eight of the registers in adjacent windows overlap, the origin of the "window" term. Registers %o0 thorugh %o7 in the caller become registers %i0 through %i7 in the called function.
On SPARC and x64, some function arguments are passed in registers, depending on how many arguments there are and their types. (The x86 architecture has no registers available for passing arguments.) On entry to a function, the parameters passed in registers might be saved on the stack, but do not necessarily need to be saved on SPARC. The Solaris ABI requires that space for the registers be allocated, but the space is not necessarily used.
In a core dump, the actual registers, particularly for functions other than the current one, are not available. The pstack operation doesn't know how many parameters a function has or what type they are. It shows the contents of the first 6 words on the stack that would hold arguments, if there were arguments, and if they were actually saved on the stack.
In optimized code on any platform, the stack area for a variable or argument is not kept up to date. Computations are kept in registers to the extent possible, and saved in memory only when necessary.
On SPARC in particular, the argument values shown in a stack trace need not be accurate.

How to understand the Vector source code for function elements()?

hello all:
This following code snippet is extracted from java.util.Vector source code.
who can tell me how i can understand what the function nextElement does?
thank you
public Enumeration elements() {
     return new Enumeration() {
         int count = 0;
         public boolean hasMoreElements() {
          return count < this.num_elem;
         public Object nextElement() {
          synchronized (Vector.this) {   //???
              if (count < elementCount) {//???
               return elementData[count++];
          throw new NoSuchElementException("Vector Enumeration");
    }

Perhaps code would help more. This codeimport java.util.Vector;
import java.util.Enumeration;
import java.util.Iterator;
public class Test {
    public static void main(String[] arghs) {
     Vector v = new Vector();
     Integer two = new Integer(2);
     // Fill the Vector
     v.add("One");
     v.add(two);
     v.add(new StringBuffer("Three"));
     // Enumerate through the objects in the vector
     System.out.println("---- Enumeration ----");
     Enumeration e = v.elements();
     while (e.hasMoreElements()) System.out.println(e.nextElement());
     // Loop through the objects in the vector
     System.out.println("---- Loop ----");
     for (int i=0; i<v.size(); i++) System.out.println(v.get(i));
     // Iterate through the objects in the vector
     System.out.println("---- Iterator ----");
     Iterator i = v.iterator();
     while (i.hasNext()) System.out.println(i.next());
}produces this output
---- Enumeration ----
One
2
Three
---- Loop ----
One
2
Three
---- Iterator ----
One
2
Three
So, for a Vector, all three do the same thing. However, Iterator is part of the Collection Framework (see [url http://java.sun.com/j2se/1.4.2/docs/guide/collections/index.html]here). This allows you to treat a whole bunch of [url http://java.sun.com/j2se/1.4.2/docs/guide/collections/reference.html]objects which implement the Collection interface all the same way. I know this is way more than you were asking, but I hope it at least clears up what you were asking.

How to understand the logic of existing code

Hi friends
I am new to java and I got the job in a company. Now they give me task to complete which use existing api developed by sr developers. Now my question is how can i understant such a large project with almost 200000 line of code.
It is web based project and using jsp and java mainly
Can anybody suggest me how can I understand it so that I can use this api and develop new code
Thanks

Use the javadoc tool to create documentation for the code.
Read the resulting documentation. Even if the senior developers didn't add any Javadoc comments (in which case, they're morons, despite being "senior"), it would be helpful just to see what the methods and classes are. In particular, look at the interfaces in the code. In well-crafted code, you get a good bird's-eye-view of the structure by looking at the interfaces and the relationships between them (in my opinion).
It's possible that the code is simply crap, in which case, you're in for a long hard slog my friend.

How to understand the FI Business Proceess

Dear Experts,
How can we understand FI Business procee of a Client. i have some BBP doc's but i couldn't.
Thanks in advace.

The ASAP solution was developed to ensure the successful, on-time delivery of a project. SAP delivers the AcceleratedSAP (ASAP) methodology for project management and system implementation.
Developed by SAP to optimize the success of implementing the SAP Business Suite, ASAP streamlines the implementation by providing templates, methods, tools, and accelerators that have been built on the success of thousands of previous SAP implementations.
The ASAP methodology adheres to a specific road map that addresses the following five general phases:
1. Project Preparation, in which the project team is identified and mobilized, the project standards are defined, and the project work environment is set up;
2. Blueprint, in which the business processes are defined and the business blueprint document is designed;
3. Realization, in which the system is configured, knowledge transfer occurs, extensive unit testing is completed, and data mappings and data requirements for migration are defined;
4. Final Preparation, in which final integration testing, stress testing, and conversion testing are conducted, and all end users are trained; and
5. Go-Live and Support, in which the data is migrated from the legacy systems, the new system is activated, and post-implementation support is provided.
ASAP incorporates standard design templates and accelerators covering every functional area within the system, as well as supporting all implementation processes. Complementing the ASAP accelerators, the project manager can create a comprehensive project plan, covering the overall project, project staffing plan, and each sub-process such as system testing, communication and data migration. Milestones are set for every work path, and progress is carefully tracked by the project management team.
Effective Communication
Weekly update meetings ensure full communication between the project team, the client project team, and project management. These meeting are used not only to update on project status, but also to identify any issues or risk areas that may threaten the project. By identifying these problems early, they are more easily mitigated and resolved, reducing their impact on the project timeline.
Ensuring Quality and Mitigating Risk
Project quality is verified near the completion of each project phase. Using existing ASAP checklists, these quality checks ensure that all tasks for the phase have been completed properly, that all relevant documentation has been kept, and that all tasks required to commence the next phase of the project have been completed.
In addition to the specific project team, companies may use Quality Assurance reviews on all of its projects to ensure that experience gained on other projects has been taken into account and that the optimum system design has been utilized.

SAP HANA - How system understands the columnar data relation?

Hi All,
SAP HANA database stores the data in columnar format. So from row based table perspective, each column will be treated as an individual table with distinct values.
How HANA database maintains the relationship of each row so the user gets correct data? In other words, how HANA database internally process the column based records?
Regards,
Mandar

Lars, Can you please help me to understand how this inverse index works here?
Mandar,
Even determination of the correct rows, can be linked to these three compression techniques.
Run-length encoding
Cluster encoding
and Dictionary encoding
Run-length encoding. If data in a column is sorted there is a high probability that two or more
elements contain the same values. Run-length encoding counts the number of consecutive column
elements with the same values. To achieve this, the original column is replaced with a two-column
list. The first column contains the values as they appear in the original table column and the second
column contains the counts of consecutive occurrences of the respective value. From this information
the original column can easily be reconstructed.
Cluster encoding. This compression technique works by searching for multiple occurrences of the
same sequence of values within the original column. The compressed column consists of a two-column
list with the first column containing the elements of a particular sequence and the second
column containing the row numbers where the sequence starts in the original column. Many popular
data compression programs use this technique to compress text files.
Dictionary encoding. Table columns which contain only a comparably small number of distinct values
can be effectively be compressed by enumerating the distinct values and storing only their numbers.
This technique requires that an additional table, the dictionary, is maintained which in the first column
contains the original values and in the second one the numbers representing the values. This
technique leads to high compression rates, is very common, e. g. in country codes or customer numbers,
but is seldom regarded as a compression technique.
thanks,
Tilak

How to understand the Xcode?

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