Run-time: :: Classification is not an extensible member variable, you can add member variables dynamically using the run-time mechanism

Run-time mechanism is pure C language, usually written OC code will eventually be converted to C run-time code

@property can only implement the declaration of Get,set method in category, can't implement the method

#import <objc/message.h>

Objc_setassociatedobject (< #id Object#>, < #const void *key#>, < #id Value#>, < #objc_ Associationpolicy policy#>)

static int heightkey;

The code is as follows:

Person.h

Run-time mechanism

//

Created by Sinting on 15-6-10.

Copyright (c) 2015 Lanou. All rights reserved.

//

#import <Foundation/Foundation.h>

@interface Person:nsobject

@property (nonatomic,assign) int age;

@end

#import "Person.h"

@implementation person

@end

#import "Person.h"

@interface person (YTT)

@property (nonatomic,assign) double height;

@end

@implementation Person (YTT)

static double Heightkey;

-(void) SetHeight: (double) height{

Objc_setassociatedobject (self, &heightkey, @ (height), objc_association_assign); Will assign the height value to the Heightkey.

}

-(double) height{

return [Objc_getassociatedobject (self, &heightkey) Doublevalue];

}

#import <Foundation/Foundation.h>

#import "Person.h"

#import "Person+ytt.h"

int main (int argc, const char * argv[]) {

@autoreleasepool {

Person *p = [[Person alloc]init];

P.height = 30;

NSLog (@ "%d", p.age);

NSLog (@ "%f", p.height);

}

return 0;

}

Results:

2015-06-10 19:30:37.743 run-time mechanism [5631:303] 0

2015-06-10 19:30:37.744 run-time mechanism [5631:303] 30.000000

Program ended with exit code:0

======================== Traversal member Variable ===========================

#import <Foundation/Foundation.h>

@interface Person:nsobject

@property (nonatomic,assign) int age;

@property (nonatomic,copy) NSString *name;

@end

#import <Foundation/Foundation.h>

#import "Person.h"

#import "Person+ytt.h"

#import <objc/runtime.h>

int main (int argc, const char * argv[]) {

@autoreleasepool {

unsigned int count = 0;

Get all member variables in the person class

Ivar *ivars = class_copyivarlist ([Person class], &count);

Traverse all member variables

for (int i = 0; i < count; i++) {

Ivar Ivar = ivars[i];

const char *name = Ivar_getname (Ivar);

const char *type = ivar_gettypeencoding (Ivar);

NSLog (@ "%s,%s", Name,type);

}

2015-06-10 19:48:39.229 run-time mechanism [5704:303] _age,i

2015-06-10 19:48:39.231 run-time mechanism [5704:303] _name,@ "NSString"

Class_copyivarlist (< #__unsafe_unretained Class Cls#>, < #unsigned int *outcount#>)

Run-time: :: Classification is not an extensible member variable, you can add member variables dynamically using the run-time mechanism