黑马程序员——Objective-C学习之不可变与可变字典(NSDictionary\NSMutableDictionary)

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一、NSDictionary

1> NSDictionary（字典）通常在给定一个关键字（通常是一个NSString字符串）下存储一个数值（可以是任何类型的对象）。然后你可以使用这个关键字查找相应的数值；

2> NSDictionary里面存储的是键值对，key----->value；

3> 常用方法：

创建字典：

+ (instancetype)dictionaryWithObjectsAndKeys:(id)firstObject, ...;

获取字典中的值：

- (id)objectForKey:(id)aKey;

二、NSMutableDictionary

1> 创建新的NSMutableDictionary对象，向类NSMutableDictionary发送dictionary消息；

2> NSMutableDictionary继承自NSDictionary；

3> NSMutableDictionary可变字典，NSDictionary不可变字典；

4> 常用方法：

添加键值对\元素：

- (void)setObject:(id)anObject forKey:(id <NSCopying>)aKey;

若对字典中已有的关键字使用setObject：forKey：方法，则用新的值替换旧值；

删除可变字典中的一个关键字：

- (void)removeObjectForKey:(id)aKey;

二、用法

//初始化        NSString *key1 = @"key1";        NSString *key2 = @"key2";        NSString *key3 = @"key3";        NSString *key4 = @"key4";        NSString *key5 = @"key5";        NSString *value1 = @"value1";        NSString *value2 = @"value2";        NSString *value3 = @"value3";        NSString *value4 = @"value4";        NSString *value5 = @"value5";        NSDictionary *dic1 = [NSDictionary dictionaryWithObject:value1 forKey:key1];        NSDictionary *dic2 = [NSDictionary dictionaryWithObjectsAndKeys:value1,key1,value2,key2, nil];        NSDictionary *dic3 = [NSDictionary dictionaryWithDictionary:dic2];        NSDictionary *dic4 = [NSDictionary dictionaryWithObjectsAndKeys:value3,key3,value4,key4,value5,key5, nil];        NSLog(@"dic1 = %@",dic1);        NSLog(@"dic2 = %@",dic2);        NSLog(@"dic3 = %@",dic3);                //获取字典数量        int size = [dic3 count];        NSLog(@"dic3 size is %d",size);                //获取value        NSString *value = [dic3 objectForKey:key1];        NSLog(@"dic3 value1 is %@",value);                //获取所有的key和value        NSArray *allKeys = [dic3 allKeys];        NSArray *allValues = [dic3 allValues];        NSLog(@"allKeys = %@",allKeys);        NSLog(@"allValues = %@",allValues);                //遍历字典        for (NSString *key in dic3) {            NSLog(@"dic3 key is %@, value is %@",key,[dic3 objectForKey:key]);        }                //--------------------------NSMutableDictionary 可变字典 -------------------------------------        //初始化        NSMutableDictionary *mDic1 = [NSMutableDictionary dictionaryWithDictionary:dic3];        NSLog(@"mDic1 = %@",mDic1);                //添加、修改、删除元素        [mDic1 setValue:value3 forKey:key3];        [mDic1 setObject:value4 forKey:key4];        [mDic1 setValue:@"value333" forKey:key3];        NSLog(@"mDic1 = %@",mDic1);        [mDic1 addEntriesFromDictionary:dic4];        NSLog(@"mDic1 = %@",mDic1);                [mDic1 removeObjectForKey:key3];        [mDic1 removeObjectForKey:key4];        [mDic1 removeObjectForKey:key5];        NSLog(@"mDic = %@",mDic1);        [mDic1 addEntriesFromDictionary:dic4];        NSLog(@"mDic = %@",mDic1);                //判断是否含有某个key        BOOL b1 = [[mDic1 allKeys] containsObject:key5];        NSLog(@"b1 = %d",b1);

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