iOS development trick-adding properties to a class using the runtime runtime method

Read some of the source code of the third-party open source class library, often found that they have added a non-existent property to a class,

For example, Pprealsidecontroller adds a Self.pprealsidecontroller attribute to Uiviewcontroller?

How did he achieve that?

1. Basic idea of realization

The first thing we need to know is that when we use a self.newproperty-like statement,

According to the rules of point syntax is actually called the Setnewproperty method, and the NewProperty method,

Then we know that he must have added a class to a uiviewcontroller, and then added a

The set and Get Methods (IBID.), so we can see here that the self.newproperty he added actually

Just a formal attribute, when you use the _newproperry is not possible!

So this form of ' attribute ' can only be invoked using the form of a point.

2. Use the runtime method to establish an association

Although we know that you can use a class to add two methods to a class, that is, an indirect property,

But how do we correlate the value of the property we need to store with it?

In the <objc/runtime.h> runtime framework provides us with a corresponding method that allows us to use a static key

Assigning a value to a piece of memory, you can also use this key to get the corresponding value

The corresponding methods are:

    Objc_setassociatedobject (self, &staticmanagerkey,                             Manager,                             Objc_association_retain);

And

Objc_getassociatedobject (self, &staticmanagerkey);

Examples of Use:

We add a manager property to a Uiviewcontroller class:

We need to create a Uiviewcontroller class with detailed code as follows:

. h

  uiviewcontroller+bbmanager.h//  huanyouwang////  Created by Mbinyang on 15/4/23.//  Copyright (c) 2015 Cc.huanyouwang. All rights reserved.//#import <UIKit/UIKit.h> #import "BBRequest.h" @interface Uiviewcontroller () @property ( strong,nonatomic) bbrequest *manager, @end @interface uiviewcontroller (Bbmanager) @end

You can see that we have added a manager property to Uiviewcontroller, which is actually the function of providing us with a Setmanager method in. h, and the manager method;

. m

  uiviewcontroller+bbmanager.m//  huanyouwang////  Created by Mbinyang on 15/4/23.//  Copyright (c) 2015 Cc.huanyouwang. All rights reserved.//#import "Uiviewcontroller+bbmanager.h" #import <objc/runtime.h> @implementation Uiviewcontroller (bbmanager) static char staticmanagerkey;-(void) Setmanager: (Bbrequest *) manager{    [self willchangevalueforkey:@ "Staticmanagerkey"];    Objc_setassociatedobject (self, &staticmanagerkey,                             Manager,                             Objc_association_retain);    [Self didchangevalueforkey:@ "Staticmanagerkey"];} -(Bbrequest *) manager{    return Objc_getassociatedobject (self, &staticmanagerkey);} @end

As you can see, we implemented the Set,get method in. M.

Using the example, we test in a Uiviewcontroller subclass:

Import in Testviewcontroller

Uiviewcontroller+bbmanager.h

Then test:

Self.manager = [[Bbrequest alloc]init];//Call set method    [Self.manager dosomething];//call  Get method

You can see that we have added a property manager for a Uiviewcontroller success.

More Original: Http://blog.csdn.net/yangbingbinga

Next: Use the runtime to highly wrap the AF and HUD

Summary: When we use the run-time method to add properties to a class, we can use it very conveniently.

iOS development trick-adding properties to a class using the runtime runtime method