//json转换成oc对象    NSString *jsonStr= @"{\"name\":\"Zhangsan\",\"age\":20,\"dog\":{\"name\":[\"XiaoHei\", \"XiaoQiang\"]}}";    NSData *data=http://www.mamicode.com/[jsonStr dataUsingEncoding:NSUTF8StringEncoding];    NSLog(@"%@",data);        NSDictionary *dic=[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];        NSLog(@"%@",dic);    NSLog(@"===%@",dic[@"age"]);    NSLog(@"%@",dic[@"dog"][@"name"]);        NSDictionary *dic2=[dic objectForKey:@"dog"];    NSLog(@"%@",dic2);    NSArray *array=[dic2 objectForKey:@"name"];    NSLog(@"%@",[array objectAtIndex:1]);       //oc对象装换成json    NSDictionary *dic3=@{@"name":@[@"liSI",@"wangWu"],@"age":@32};    NSData *data2=[NSJSONSerialization dataWithJSONObject:dic3 options:NSJSONWritingPrettyPrinted error:nil ];    NSString *str2=[[NSString alloc]initWithData:data2 encoding:NSUTF8StringEncoding];    NSLog(@"%@",str2);    NSObject类中的+ (BOOL)instancesRespondToSelector:(SEL)aSelector用于判断某类中是否实现了某实例方法URI 统一资源URL 统一资源标识符异步请求是不会等待的，同步是要等待的执行完才执行下一代码、、、、、、、、、网络请求、、、、、、、////  ViewController.m//  NSObjc-0804////  Created by apple on 14-8-4.//  Copyright (c) 2014年 apple. All rights reserved.//#import "ViewController.h"#import "Ketter.h"@interface ViewController ()            @end@implementation ViewController            - (void)viewDidLoad {    [super viewDidLoad];//    Ketter *k=[[Ketter alloc]init];    NSURL *url=[NSURL URLWithString:@"http://www.baidu.com/"];    NSLog(@"%@   %@",[url host],[url scheme]);    NSURL *url2=[NSURL URLWithString:@"../../../" relativeToURL:url];    NSLog(@"%@",url2);        NSURLRequest *request=[NSURLRequest requestWithURL:url];    NSLog(@"%@",[request HTTPMethod]);    NSLog(@"%@",[request allHTTPHeaderFields]);        //获取请求地址    NSLog(@"%@",[request URL]);        [request cachePolicy];        NSData *data=http://www.mamicode.com/[NSData dataWithContentsOfURL:url];    NSLog(@"%d",data.length);        //同步方法    //调用一个方法的时候，如果该方法的返回依赖于它的功能是否完成，称为同步方法//    NSData *data2=[NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {        NSLog(@"%d",data.length);    }];        NSLog(@"======%@",request);   // NSString}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@endjson就是一个字符chuan///////////////////////////////////////////////////////////// Kitty *k = [[Kitty alloc] init];    [k print];        //@selector(print) : myPrint        //1. 运行时替换Kitty中print方法的实现    class_replaceMethod([Kitty class], @selector(print), myPrint, NULL);    //给k对象发送@selector(print)消息//    [k print];        class_addMethod([Kitty class], @selector(printx), myPrint, NULL);    [k performSelector:@selector(printx)];        //动态语言    //swizzing        //Objective-C方法的调用，发送消息    objc_msgSend(k, @selector(print));        //获取的是实例方法    IMP call = [k methodForSelector:@selector(call)];//    call(k, @selector(call));        //子类的对象调用子类方法的实现    SonKitty *son = [[SonKitty alloc] init];    [son print];        //本质上，用%@打印对象的时候，打印的是该对象调用description方法所返回的字符串    NSLog(@"%@:%@", [son description], son);        NSArray *array = @[@13, @"35", son];    NSLog(@"%@", array);        UIView *v = [[UIView alloc] init];    NSLog(@"%@", v);        //isKindOfClass匹配子类和父类的对象    //isMemberOfClass严格匹配类型    if (![son isMemberOfClass:[Kitty class]]) {        NSLog(@"v is not kind of Kitty");    }    else {        NSLog(@"v is kind of Kitty");    }