On 64bit iOS 8.1 simulator, Why BOOL type function return a unexpected value?

Question

Code example:
------func.h------
#import <Foundation/Foundation.h>
@interface func ： NSObject
+ (id)instance;
@end
------func.m------
#import "func.h"
@implementation func
+ (id)instance
     static func *obj = nil;
     if (obj == nil) {
          obj = [func new];
     return obj;
- (BOOL)test
     return YES;
@end
I created a new class "func" in project as above shown, set the project compile scheme to "release" mode.
I found that if I call  [func test] method from another class, its return value is not "1" on iPhone6 simulator, it is a random value. Why?
PS: I can not find this problem on iPhone6 device, it seems only happen on 64 bit simulator. Why?

Answer 1

Your main problem as etresoft points out, is that your trying to use -test as a class method, you'll need to declare it as:
+test { ... }
for this to work. -test and +test are two different kinds of methods, -test needs a instance of 'func' to work:
func *f = [[func alloc] init]; // create instance f of func
[f test]; // calls -test, -test can use f as self
while +test needs a class (name):
[func test]; // calls +test
Class methods are mainly used for creating/initiating instances of a class, the +init method is a typical example of this, other uses are are for utility methods that may not really be tied to a specific object (class instance). Also note that a class method doesn't have access to self as it wasn't called on an object, so data will need to be passed in via parameters or by using global variables.
===============
dispatch_once() is the recommended way to do singletons, although the above will typically work assuming that its not accessed by multiple threads, e.g. is only used on the main thread.
===============
This page http://www.bignerdranch.com/blog/bools-sharp-corners/ appears to relate to etrsofts dislike for BOOL (the standard boolean type of Objective-C) and his preference for bool (the C++ variant), but as the page mentions: "Update October 2013 - On 64-bit iOS (device and simulator) BOOL is now actually bool, so the sharp corners have thankfully gone away for that platform. For everything else, though…"