Objective-C Primer（2）Private Methods and Class Properties

Objective-C Primer（2）Private Methods and Class Properties

• Author: 柳大·Poechant（钟超）
• Email: zhongchao.ustc#gmail.com (# -> @)
• Blog: Blog.youkuaiyun.com/Poechant
• Date: May 6^th, 2012

1 What the relationship between C and Objective-C?

If you want, you can just program in C language style and syntax, and there will be no error or warning if you never make mistakes of C programming. Therefore, you must say: Getcha!

Yes! Objective-C is a super set of C language, just like C++ to C.

2 No private methods declaration in .h file?

Yes, you are right. But think it twice. Is it more reasonable to hide or ignore private methods declaration in header file? Every invoker just appears in member methods of .m source code files, so it’s unnecessary to give any clue for private methods in header file.

Do you know how to hide private methods declaration in C++? (Give you a hint: pimpl idiom.)

Now I will show how to do that. The .h is still the one I introduce in Objective-C Primer (1) Get started! But how about .m file?

//
//  TestClass.m
//  ObjectiveCTest
//
//  Created by 超 钟 on 12-5-6.
//  Copyright (c) 2012年 http://blog.youkuaiyun.com/poechant. All rights reserved.
//

#import "TestClass.h"

@implementation TestClass
@synthesize foo;

-(void)privateMethod
{
    NSLog(@"I'm a priavte method, named 1");
}

-(void)someMethod
{
    NSLog(@"some method got called");
    [self privateMethod];
}

But notice that there will be a warning if you invoke a private method below the invoker method. Just like the following.

3 Class properties

As we know at present, in Objective-C, a class consists of an interface which is visible for external users and an implementation for class behavior details.

What about properties?

There are some many identifiers for properties, which will be messed up.

• retain will increase the reference counter, and of course set the value of the pointer.
• assign does not increate the reference counter, but also set the value of the pointer.
• copy will create a new object, which is the same as the source object. But this new object has its own new reference counter.

You should notice that any two of these three identifier could not be used together.

• nonatomic means this object is not thread safe. So you must guess it. Yes! If you do not use nonatomicand just use the default, the object will be thread safe and there will be scoped lock used internally.

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