iOS-NSDictionary与NSMutableDictionary详解

竹林风

NSDictionary

1.NSDictionary初始化


1)字典中元素是键值对,所以字典元素都是成对出现的,一个元素就是一对(有key和对应的value)
2)键和值都是对象类型,键和值的类型可以不同
3)在字典中,不能出现相同的key,但可以出现相同的value,key的唯一性,这样就能够通过key唯一确定value

[Objective-C] 纯文本查看 复制代码

//不可变字典:字典对象一旦创建完成后,字典成员不能够被修改,增加和删除
    NSDictionary *dictionary = @{@"key1":@"value1", @"key2":@"value2"};
    //常用//初始化不可变字典//字典中的元素是成对出现的，要有key和value//key:value
#pragma mark 对象方法创建字典
    NSDictionary *dictionary1 = [[NSDictionary alloc] initWithDictionary:dictionary];
    //用其他字典初始化当前的字典对象
    //字典中的key和value可以是任意的oc类型//nil:字典的结束标志
    NSDictionary *dictionary2 = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1",
                                 @"value2", @"key2", nil];
    //value在前key在后，成对出现//最常用
#pragma mark 类方法创建字典
    NSDictionary *dictionary3 = [NSDictionary dictionaryWithDictionary:dictionary];
    NSDictionary *dictionary4 = [NSDictionary dictionaryWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil];
    
    NSLog(@"dictionary===%@",dictionary);
    NSLog(@"dictionary1===%@",dictionary1);
    NSLog(@"dictionary2===%@",dictionary2);
    NSLog(@"dictionary3===%@",dictionary3);
    NSLog(@"dictionary4===%@",dictionary4);

2.NSDictionary的操作

[Objective-C] 纯文本查看 复制代码

//    字典中元素个数
    NSInteger count = dictionary.count;
    NSLog(@"dictionary的数量为%@",@(count));
    
//    //根据key(索引)找value(值)
    NSString *value1 = dictionary[@"key1"];
    NSLog(@"dictionary中关键字key1对应的值为%@",value1);
    
    //获取字典中的所有的key
    NSArray *aryKey = [dictionary allKeys];
    NSLog(@"字典dictionary的所有关键字是%@",aryKey);
    
    //获取字典中所有的value
    
    //第一种写法
    for (NSString *key in [dictionary allKeys]) {
        NSString *value = [dictionary objectForKey:key];
        NSLog(@"关键字key为%@对应的值为%@",key,value);
    }
    //第二种写法
    NSLog(@"dictionary的所有值为%@",[dictionary allValues]);
    
//    获取某个值value对应的所有键key
    
    NSArray *keys = [dictionary allKeysForObject:@"value1"];
    NSLog(@"dictionary值为value1对应的所有关键字为%@",keys);

打印结果：




NSMutableDictionary


1. NSMutableDictionary初始化

[Objective-C] 纯文本查看 复制代码

NSMutableDictionary *mdictionary = [NSMutableDictionary dictionaryWithCapacity:0];//创建一个空字典

2.NSDictionary的操作

[Objective-C] 纯文本查看 复制代码

//- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;
    //作用：字典的末尾追加元素
    [mdictionary setObject:@"苹果" forKey:@"name"];
    [mdictionary setObject:@"脆甜的苹果" forKey:@"info"];
    NSLog(@"末尾追加元素的mdictionary%@",mdictionary);
    
    //- (void)addEntriesFromDictionary:(NSDictionary *)otherDictionary;
    //作用：字典末尾追加一个字典
    NSDictionary *dic = @{@"egname": @"apple"};
    [mdictionary addEntriesFromDictionary:dic];
    NSLog(@"末尾了一个字典的mdictionary%@",mdictionary);
    
    //    字典中元素的修改
    //- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;
    //作用：key值字典中已经存在，进行覆盖，如果不存在，追加
    [mdictionary setObject:@"坏苹果" forKey:@"info"];
    NSLog(@"修改字典mdictionary的键为info的值为坏苹果%@",mdictionary);
    
    //- (void)setDictionary:(NSDictionary *)otherDictionary;
    //作用：替换字典
    NSDictionary *dic1 = @{@"name": @"apple"};
    [mdictionary setDictionary:dic1];
    NSLog(@"替换字典mdictionary为dic1%@",mdictionary);
    
//    字典中元素的删除(删除操作)
    NSMutableDictionary *mdictionary1 = [NSMutableDictionary dictionaryWithCapacity:0];
    
    [mdictionary1 setObject:@"香蕉" forKey:@"name"];
    [mdictionary1 setObject:@"没熟的香蕉" forKey:@"info"];

    //- (void)removeObjectForKey:(id)aKey;
    //作用：根据key删除对应的元素
    [mdictionary1 removeObjectForKey:@"info"];//常用
    NSLog(@"删除字典mdictionary1中key为info的值%@",mdictionary1);
    
    //删除所有的元素
    [mdictionary1 removeAllObjects];
    NSLog(@"字典mdictionary1删除了所有的值%@",mdictionary1);
    

运行结果：



附件： Test-NSDictionary.zip (155.42 KB, 下载次数: 0)

2018-12-6 15:57 上传

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