NSDictionary

字典用于保存具有映射关系数据的集合

一个key—value对认为是一个条目（entry），字典是存储key—value对的容器

与数组不同，字典靠key存取元素

key不能重复，value必须是对象

键值对在字典中是无序存储的

字典分：不可变字典（NSDictionary）和可变字典（NSMutableDictionary）

不可变字典一旦创建，键值对就不可更改，不可添加，不可删除，仅能读取key或者value

常用方法有：

1、创建字典对象

2、获取所有key值，获取所有value值

3、通过key值查询value

1、常见字典的常用方法

在创建字典对象时需要赋值键值对，但是顺序为：值，键，（值在前键在后的形式）

    NSDictionary *dic1 = [[NSDictionary alloc] initWithObjectsAndKeys:@"Duke",@"name",@33,@"age",@"男",@"gender", nil];
    NSLog(@"%@",dic1);
    NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:@"Duke",@"name",@33,@"age",@"男",@"gender", nil];
    NSLog(@"%@",dic2);
    NSArray *keys = @[@"name",@"age",@"gender"];

    NSArray *values = @[@"Duke",@33,@"male"];

字典的语法糖形式

键值对之间以逗号隔开，键和值之间以冒号隔开

    NSDictionary *dic5 = @{@"name" : @"Duke",@"age" : @33,@"gender" : @"male"};

    NSLog(@"%@",dic5);

创建字典对象时两个数组元素个数必须一致

    NSDictionary *dic3 = [[NSDictionary alloc] initWithObjects:values forKeys:keys];
    NSLog(@"%@",dic3);
    NSDictionary *dic4 = [NSDictionary dictionaryWithObjects:values forKeys:keys];

    NSLog(@"%@",dic4);

通过count方法获取字典中键值对的个数

    NSInteger count = [dic4 count];

    NSLog(@"%ld",count);

获取字典中所有的键

    NSArray *allKeys = [dic4 allKeys];

    NSLog(@"%@",allKeys);

获取字典中所有的值组成的值

    NSArray *allValues = [dic4 allValues];

    NSLog(@"%@",allValues);

通过指定的键获取其在字典中对应的值

    id object = [dic4 objectForKey:@"age"];
    NSLog(@"%@",object);

    for (int i = 0; i < count; i++) {
        id key = [allKeys objectAtIndex:i];

根据当前遍历得到的key去获取对应的value

        id value = [dic4 objectForKey:key];
        NSString *result = [value isKindOfClass:[NSString class]] ? @"YES" : @"NO";
        NSLog(@"%@:%@-->%@",key,value,result);

    }

 

• 字典初始化

void arrayTest5()
{
    //字典初始化方式1
    NSDictionary *dictionary1 = [[NSDictionary alloc]initWithObjectsAndKeys:@"value0",@"key0",
                                                                           @"value1",@"key1",
                                                                           @"value2",@"key2",
                                                                           @"value3",@"key3",
                                                                           @"value4",@"key4",
                                                                           nil];
    
    NSLog(@"%@",dictionary1);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
    
    
    //字典初始化方式2
    NSArray *valueArray = @[@"value0",@"value1",@"value2",@"value3",@"value4"];
    NSArray *keyArray = @[@"key0",@"key1",@"key2",@"key3",@"key4"];
    NSDictionary *dictionary2 = [[NSDictionary alloc]initWithObjects:valueArray forKeys:keyArray];
    NSLog(@"%@",dictionary2);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
    
    
    //字典初始化方式3
    NSDictionary *dictionary3 = @{
                                 @"key0":@"value0",
                                 @"key1":@"value1",
                                 @"key2":@"value2",
                                 @"key3":@"value3",
                                 @"key4":@"value4"
                                 };
    NSLog(@"%@",dictionary3);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
    
    
    //调用NSDictionary静态方法生成字典
    NSDictionary *dictionary4 = [NSDictionary dictionaryWithObject:@"value0" forKey:@"key0"];
    NSLog(@"%@",dictionary4);
    /*
     {
     key0 = value0;
     }
     */
    
    
    NSDictionary *dictionary5 = [NSDictionary dictionaryWithObjects:valueArray forKeys:keyArray];
    NSLog(@"%@",dictionary5);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
    
    NSDictionary *dictionary6 = [NSDictionary dictionaryWithObjectsAndKeys:@"value0",@"key0",@"value1",@"key1",@"value2",@"key2",@"value3",@"key3",@"value4",@"key4", nil];
    NSLog(@"%@",dictionary6);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
}

• 字典基本常用用法

void arrayTest6()
{
    NSDictionary *dictionary1 = [[NSDictionary alloc]initWithObjectsAndKeys:@"value0",@"key0",
                                 @"value1",@"key1",
                                 @"value2",@"key2",
                                 @"value3",@"key3",
                                 @"value4",@"key4",
                                 @"value4",@"key5",
                                 nil];
    NSLog(@"%@",dictionary1);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value4
     }
     */
    
    NSLog(@"%ld",dictionary1.count);
    /* 5 */
    
    //输出特定元素
    NSLog(@"%@",dictionary1[@"key0"]);
    NSLog(@"%@",[dictionary1 objectForKey:@"key0"]);
    /* value0 */
    
    //获取所有key
    NSLog(@"%@",dictionary1.allKeys);
    /*
     (
     key3,
     key1,
     key4,
     key2,
     key0
     )
     */
    
    //获取所有value
    NSLog(@"%@",dictionary1.allValues);
    /*
     (
     value3,
     value1,
     value4,
     value2,
     value0
     )
     */
    
    //获取特定value对应的所有key
    NSLog(@"%@",[dictionary1 allKeysForObject:@"value4"]);
    /*
     (
     key4,
     key5
     )
     */
    
    //分别获取key对应的value,对于不存在的key，返回"not found"
    NSLog(@"%@",[dictionary1 objectsForKeys:@[@"key0",@"key1",@"key8"] notFoundMarker:@"not found"]);
    /*
     (
     value0,
     value1,
     "not found"
     )
     */
    
    NSDictionary *dictionaryOther = @{@"key0":@"value0"};
    BOOL result = [dictionary1 isEqualToDictionary:dictionaryOther];
    NSLog(@"%hhd",result);
    /* 0 */
    
    //保存到本地文件
    [dictionary1 writeToFile:@"/Users/new/Desktop/dictionary.txt" atomically:YES];
    /*
     <?xml version="1.0" encoding="UTF-8"?>
     <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
     <plist version="1.0">
     <dict>
     <key>key0</key>
     <string>value0</string>
     <key>key1</key>
     <string>value1</string>
     <key>key2</key>
     <string>value2</string>
     <key>key3</key>
     <string>value3</string>
     <key>key4</key>
     <string>value4</string>
     <key>key5</key>
     <string>value4</string>
     </dict>
     </plist>
     */
    
    //读取本地文件，反序列化为字典
    NSDictionary* dictionary2 = [NSDictionary dictionaryWithContentsOfFile:@"/Users/new/Desktop/dictionary.txt"];
    NSLog(@"%@",dictionary2);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value4;
     }
     */
    
    //修改字典元素值,如果key存在，则修改对应的value,如果key不存在，则插入一个新元素
    [dictionary2 setValue:@"update value0" forKey:@"key0"];
    NSLog(@"%@",dictionary2);
    /*
     {
     key0 = "update value0";
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value4;
     }
     */
    
    //插入一个新元素，该key不存在
    [dictionary2 setValue:@"key not found" forKey:@"noKey"];
    NSLog(@"%@",dictionary2);
    /*
     {
     key0 = "update value0";
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value4;
     noKey = "key not found";
     }
     */
}

• NSDictionary遍历

void dictionaryTest()
{
    NSDictionary *dictionary1 = [[NSDictionary alloc]initWithObjectsAndKeys:@"value0",@"key0",
                                 @"value1",@"key1",
                                 @"value2",@"key2",
                                 @"value3",@"key3",
                                 @"value4",@"key4",
                                 @"value4",@"key5",
                                 nil];
    //遍历方法一
    for (NSString *key in dictionary1) {
        NSLog(@"%@ = %@",key,dictionary1[key]);
    }
    /*
     key3 = value3
     key1 = value1
     key4 = value4
     key2 = value2
     key0 = value0
     key5 = value5
     */
    
    
    //遍历方法二
    //NSEnumerator *objectEnumerator = [dictionary1 objectEnumerator];    //objectEnumerator获取value枚举
    NSEnumerator *keyEumerator = [dictionary1 keyEnumerator];           //keyEnumerator获取key枚举
    NSString *key = nil;
    while (key = [keyEumerator nextObject]) {
        NSLog(@"%@ = %@",key,dictionary1[key]);
    }
    /*
     key3 = value3
     key1 = value1
     key4 = value4
     key2 = value2
     key0 = value0
     key5 = value5
     */
    
    //遍历方法三
    [dictionary1 enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        NSLog(@"%@ = %@",key,obj);
    }];
    /*
     key3 = value3
     key1 = value1
     key4 = value4
     key2 = value2
     key0 = value0
     key5 = value5
     */
    
}

 

• NSMutableDictionary

NSMutableDictionary继承于NSDictionary，在此基础上新增加对元素新增、删除、更新等操作，如下代码演示

void mutableDictionaryTest()
{
    NSMutableDictionary *mutableDictionary = [[NSMutableDictionary alloc]initWithCapacity:7];
    NSLog(@"%ld",mutableDictionary.count);
    /* 0 */
    [mutableDictionary setValue:@"value0" forKey:@"key0"];
    [mutableDictionary setValue:@"value1" forKey:@"key1"];
    [mutableDictionary setValue:@"value2" forKey:@"key2"];
    [mutableDictionary setValue:@"value3" forKey:@"key3"];
    [mutableDictionary setValue:@"value4" forKey:@"key4"];
    [mutableDictionary setValue:@"value5" forKey:@"key5"];
    [mutableDictionary setValue:@"value6" forKey:@"key6"];
    [mutableDictionary setValue:@"value7" forKey:@"key7"];
    NSLog(@"%ld",mutableDictionary.count);
    /* 8 */
    NSLog(@"%@",mutableDictionary);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value5;
     key6 = value6;
     key7 = value7;
     key8 = value8;
     }
     */
    
    
    //删除元素
    [mutableDictionary removeObjectForKey:@"key7"];
    NSLog(@"%ld",mutableDictionary.count);
    /* 7 */
    NSLog(@"%@",mutableDictionary);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     key5 = value5;
     key6 = value6;
     }
     */
    
    //对于key存在，则修改对应的value,否则添加新元素
    [mutableDictionary setValue:@"update value6" forKey:@"key6"];
    NSLog(@"%@",mutableDictionary);
    
    //移除多个key对应的元素
    [mutableDictionary removeObjectsForKeys:@[@"key6",@"key5"]];
    NSLog(@"%@",mutableDictionary);
    /*
     {
     key0 = value0;
     key1 = value1;
     key2 = value2;
     key3 = value3;
     key4 = value4;
     }
     */
    
    //移除所有元素
    [mutableDictionary removeAllObjects];
    NSLog(@"%ld",mutableDictionary.count);
    /* 0 */
}