[RunTime练习二]属性的遍历

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface MyTestObj : UIButton

@property (nonatomic,retain) NSNumber* MyNumber;
@property (nonatomic) NSInteger MyInteger;
@property (nonatomic, readwrite, copy) NSString* MyString;
@property (nonatomic,retain)NSMutableArray* MyArray;
@property (nonatomic,retain)NSMutableDictionary* MyDictionary;
@end

#import "MyTestObj.h"

@implementation MyTestObj

-(instancetype) init
{
if (self = [super init]) {
self.MyArray = [[NSMutableArray alloc] initWithObjects:@"hello", nil];
self.MyDictionary = [[NSMutableDictionary alloc]initWithCapacity:1];
[self.MyDictionary setObject:@"hello" forKey:@"world"];
self.MyString = @"hello world";
self.MyNumber = [NSNumber numberWithInteger:100];
self.MyInteger = 80;
}
return  self;
}
@end

#import "ViewController.h"
#import "MyTestObj.h"
#import <objc/runtime.h>

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
MyTestObj* M = [[MyTestObj alloc] init];
NSInvocation* invoc ;
unsigned PropertiesCount = 0;
objc_property_t* properties = class_copyPropertyList([M class], &PropertiesCount);
for (int i = 0; i < PropertiesCount; i++) {
@autoreleasepool {
objc_property_t prop = properties[i];
NSString* propName = [NSMutableString stringWithFormat:@"%s",property_getName(prop)];
SEL s = NSSelectorFromString(propName);
//sign和invoc都只能通过类方法得到(可能有别的，我不太清楚～)，写在for循环里面浪费了～～
NSMethodSignature* sign = [[M class] instanceMethodSignatureForSelector:s];
invoc = [NSInvocation invocationWithMethodSignature:sign];
[invoc setSelector:s];
[invoc setTarget:M];
[invoc invoke];
if (strcmp([sign methodReturnType], @encode(void)) == 0) {
NSLog(@"Return None~");
}
else if (strcmp([sign methodReturnType], @encode(NSInteger)) == 0)
{
void* pValue = (void*)malloc([sign methodReturnLength]);
[invoc getReturnValue:pValue];
id result = [NSNumber numberWithInteger:*((NSInteger*)pValue)];
NSLog(@"Ruturn NSInteger %@",result);
}
else
{
void* pValue = (void*)malloc([sign methodReturnLength]);
[invoc getReturnValue:&pValue];
id result = (__bridge id)pValue;
NSLog(@"Return object %@",result);
}

}
}
// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

1，可以遍历对象对应类的某一层次的所有属性（只写属性没考虑～）。

2，instanceMethodSignatureForSelector，不仅能获取方法的签名，也能获取属性的签名，再次印证了，@property声明的属性，读取方法就是属性名。

3，nsinvocation在调用的时候，即使是返回值，也会release,所以如果不申请内存，来放返回值，那么oc对象的引用计数就混乱了。retainArguments只retain了参数。

上面的这些操作完全是为了巩固下nsinvocation的用法，获取属性值，完全可以用［M ValueForKey:propName］来完成～～

参考：http://www.cnblogs.com/pengyingh/articles/2359199.html