OC菜鸟成长记-OC中的字典

最新推荐文章于 2021-04-25 17:41:27 发布

LiuYongM

最新推荐文章于 2021-04-25 17:41:27 发布

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分类专栏： OC菜鸟成长笔记文章标签： NSDictionary NSMutableDicitonary OC字典

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本文深入探讨了Objective-C (OC) 中字典的基本概念，包括不可变字典 (NSDictionary) 和可变字典 (NSMutableDictionary) 的初始化、访问、修改、删除等操作，并通过实例展示了其用法。

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下面笔者对自己有关OC中的字典的知识进行一下总结。在OC当中，字典的基本元素是由键和值组成的键值对。字典有不可变字典(NSDictionary)和可变字典(NSMutableDicitonary)两种。

首先是不可变字典(NSDictionary):

        //初始化
        NSDictionary *d1=[NSDictionary new];
        NSDictionary *d2=[NSDictionary dictionaryWithObject:@"abcdefg" forKey:@"zimu"];
        NSDictionary *d3=[NSDictionary dictionaryWithObjectsAndKeys:@"a",@"zimu",@"b",@"zimu",@"c",@"zimu", nil];
        NSDictionary *d5=[NSDictionary dictionaryWithDictionary:d3];
        //新语法
        NSDictionary *d6=@{@"zimu":@"a",@"zimu":@"b"};
        
        //键值对的数量
        NSUInteger dcount = d3.count;
        NSLog(@"dcount=%lu",dcount);
        
        //访问字典
        NSString *zimu=[d3 objectForKey:@"zimu"];
        NSLog(@"zimu = %@ ",zimu);//字典中不存在相同的key
        NSString *zimu2 =[d2 objectForKey:@"zimu"];
        NSLog(@"zimu2=%@",zimu2);
        
        //历遍字典
        //字典有两部分：key和value
        //需要使用数组进行接收
        NSArray *dictionaryKey=d3.allKeys;
        NSArray *dictionaryValue=d3.allValues;
        for (id dkey in dictionaryKey) {
            NSLog(@"dkey=%@",dkey);
        }
        NSEnumerator *denumerator = [dictionaryValue objectEnumerator];
        id dobj;
        while (dobj =[denumerator nextObject]) {
            NSLog(@"dobj=%@",dobj);
        }

运行结果是:

 oc_731_practise[17787:164553] dcount=1
 oc_731_practise[17787:164553] zimu = a 
 oc_731_practise[17787:164553] zimu2=abcdefg
 oc_731_practise[17787:164553] dkey=zimu
 oc_731_practise[17787:164553] dobj=a

然后是可变字典(NSMutableDicitonary):

//        NSMutableDictionary
        //初始化
        NSMutableDictionary *md1=[[NSMutableDictionary alloc]init];
        NSMutableDictionary *md2=[NSMutableDictionary dictionaryWithDictionary:d3];
        NSMutableDictionary *md3=[NSMutableDictionary dictionaryWithObjectsAndKeys:@20,@"length",@10,@"width", nil];
        
        //修改、增加
        [md3 setObject:@30 forKey:@"height"];
        NSLog(@"md3=%@",md3);
        [md3 setObject:@60 forKey:@"length"];
        NSLog(@"md3=%@",md3);
        md3[@"width"]=@100;//新语法进行修改
        NSLog(@"md3=%@",md3);
        md3[@"point"]=@0;
        NSLog(@"md3=%@",md3);//新语法进行添加
        
        //删除
        [md3 removeObjectForKey:@"point"];//删除一个元素 (键point 对应的值)
        NSLog(@"md3=%@",md3);
        [md3 removeObjectsForKeys:@[@"point",@"length"]];//删除多个元素 (键point 和length对应的值)
        NSLog(@"md3=%@",md3);
        [md3 removeAllObjects];//删除所有元素
        NSLog(@"md3=%@",md3);

运行结果是:

 oc_731_practise[17787:164553] md3={
    height = 30;
    length = 20;
    width = 10;
}
 oc_731_practise[17787:164553] md3={
    height = 30;
    length = 60;
    width = 10;
}
 oc_731_practise[17787:164553] md3={
    height = 30;
    length = 60;
    width = 100;
}
 oc_731_practise[17787:164553] md3={
    height = 30;
    length = 60;
    point = 0;
    width = 100;
}
 oc_731_practise[17787:164553] md3={
    height = 30;
    length = 60;
    width = 100;
}
 oc_731_practise[17787:164553] md3={
    height = 30;
    width = 100;
}
 oc_731_practise[17787:164553] md3={
}