IOS runtime Dynamic Runtime two

There are compile-time polymorphic and run-time polymorphism in C #, Java, and only runtime polymorphism in OC, which is related to its operating mechanism. In OC, the invocation of a method is done through the delivery of the message. In the iOS runtime Dynamic runtime, a http://www.cnblogs.com/5ishare/p/4708647.html is mainly about the next run-time process, which mainly looks at message forwarding (the basis for polymorphism).

I. INTRODUCTION

There are two .h,<objc/runtime.h> and <objc/message.h> in the <objc/objc-runtime.h>, this article mainly understands <objc/message.h>

Two. Message forwarding

In this class there are mainly 3 Chinese law (other kinds I do not know so there are 3 kinds): Objc_msgsend, Objc_msgsendsuper, Method_invoke.

Like Objc_msgsend_stret, Objc_msgsend_fpret function returns struct, floating-point number these need to go through the CPU special processing, so do not be too careful. These are the 3 variants above, and when the structure, floating-point numbers are returned, they are called _stret, _fpret.

Three. Use of methods

There are a few points to note before using:

1. To introduce frames <objc/objc-runtime.h>

2. Direct write run-time code will be the error needs to press set

1). objc_msgsend

In the iOS runtime Dynamic Runtime, a blog also writes that the method call in OC is actually converted to Objc_msgsend for message forwarding.

2). Objc_msgsendsuper

This is to forward the message to the parent class. The first parameter of a method is a struct of type objc_super. The structure consists of two variables:

1.receiver: The actual recipient of the message

2.superClass: Pointer to the parent class of the current class

struct objc_super {        //  Specifies an instance of a class.       __unsafe_unretained  ID  receiver;         /// specifies the particular superclass of the instance to message.        __unsafe_unretained Class super_class;    };

ID objc_msgsendsuper (struct objc_super *super, SEL op, ...)

3). Method_invoke

There is invoke in C # multi-threading, which is similar to C # for invocation of methods. It is necessary to transfer the structure method. A method in a class can be obtained by runtime.h

Method_invoke (ID

Iv. test Results

A Father class and a son that inherits father are created in the project. The Son class overrides the parent class's-(NSString *) getnamewithfamily: (NSString *) Family method.

#import <Foundation/Foundation.h>@interface  father:nsobject-(NSString *) Getnamewithfamily: (NSString *) family; @end

////FATHER.M//RunTime////Created by City--online on 15/11/24.//copyright©2015 year City--online. All rights reserved.//#import "Father.h"@implementationFather-(NSString *) getnamewithfamily: (NSString *) family; {    return[NSString stringWithFormat:@"Father%@", family];}@end

// //   Son.h//  RunTime////  Created by city--online on 15/ 11/24. //   copyright©2015 year city--online. All rights reserved. // #import " Father.h " @interface Son:father @end

////son.m//RunTime////Created by City--online on 15/11/24.//copyright©2015 year City--online. All rights reserved.//#import "Son.h"@implementationSon-(nsstring*) getnamewithfamily: (NSString *) family{return[NSString stringWithFormat:@"Son%@", family];}@end

1.objc_msgsend calls son's getnamewithfamily by Objc_msgsend: The method returns as a string, a parameter

    Son *son=[[son Alloc]init];     *name= Objc_msgsend (son, @selector (getnamewithfamily:),@ "Tom");    NSLog (@ "%@", name);

-One-up: £ º26.705 runtime[6514:223611 ] Son Tom

2.objc_msgsendsuper calls the parent class through objc_msgsendsuper like [super XXXXX], primarily the first objc_super type of struct.

 struct   Objc_super Objcsuper;    Objcsuper.receiver  =father;        Objcsuper.super_class  =[son superclass]; NSString  *supername=objc_msgsendsuper (&objcsuper, @selector (getnamewithfamily:), @ " cui   "    ); NSLog ( @ " %@  , supername); 

-One-up: £ º26.705 runtime[6514:223611 ] Father Cui

3.method_invoke

class ], @selector (getnamewithfamily:));     *invokename= Method_invoke (Son,method,@ "Zhao");    NSLog (@ "%@", Invokename);

-One-up: £ º26.705 runtime[6514:223611 ] Son Zhao

    class ], @selector (getnamewithfamily:));     *invokename= Method_invoke (Father,method,@ "Zhao");    NSLog (@ "%@", Invokename);

£ º:28.288 runtime[6546:231306 ] Father Zhao

IOS runtime Dynamic Runtime two