OC基础 可变字典与不可变字典的使用

1.不可变字典

1.1创建不可变字典

        //创建字典

        //注意:

        //1，元素个数是偶数

        //2，每两个元素是一个键值对

        //3，值在前，键在后

        NSDictionary *dic = [[NSDictionary alloc] initWithObjectsAndKeys:@"huang",@"name",@"",@"age", nil];

        NSLog(@"%@",dic);

        //用一个字典来创建另外一个字典

        NSDictionary *dic2 = [[NSDictionary alloc] initWithDictionary:dic];

        //注意:

        //1,value和key的个数要相同

        //2,values和keys里面的元素的先后顺序要对应

        NSDictionary *dic3 = [[NSDictionary alloc] initWithObjects:[NSArray arrayWithObjects:@"huang",@"", nil] forKeys:[NSArray arrayWithObjects:@"name",@"age", nil]];

        NSLog(@"%@",dic3);

        //创建数组的新方式

        NSArray *arr = @[@"",@"",@""];

        NSDictionary *dic4 = [NSDictionary dictionaryWithObjectsAndKeys:@"",@"age",@"huang",@"name", nil];

        NSDictionary *dic5 = [NSDictionary dictionaryWithDictionary:dic4];

        NSDictionary *dic6 = [NSDictionary dictionaryWithObjects:@[@"huang",@""] forKeys:@[@"name",@"age"]];

        //创建字典的新方式

        NSDictionary *dic7 = @{@"name": @"huang",@"age":@""};

1.2不可变字典的常用操作

        //字典的常用操作

        NSInteger count = [dic7 count];

        NSLog(@"%ld",count);

        //根据键去获取值

        NSString *str = [dic7 valueForKey:@"name"];

        NSLog(@"%@",str);

        //获取所有的key

        NSArray *allKeys = [dic7 allKeys];

        NSLog(@"%@",allKeys);

        //获取所有的value

        NSArray *allValues = [dic7 allValues];

        //获取一个value对应的key

        NSDictionary *dic8 = @{@"name":@"huang",@"age":@"",@"score":@""};

        NSArray *arr1 = [dic8 allKeysForObject:@""];

        NSLog(@"%@",arr1);

        NSDictionary *dic9 = @{@"dic8":dic8,@"dic7":dic7};

        NSLog(@"%@",dic9);

        //数组与字典的嵌套

        NSArray *array1 = @[@"",@"",@""];

        NSDictionary *dictionary1 = @{@"name":@"xiaoming",@"age":@""};

        NSDictionary *dictionary2 = @{@"array":array1,@"dictionary":dictionary1};

        NSLog(@"%@",dictionary2);

        NSArray *array2 = @[array1,dictionary1];

        NSLog(@"%@",array2);

        //字典的遍历

        NSDictionary *dictionary3 = @{@"name":@"huang",@"age":@"",@"number":@""};

        NSArray *allKeys1 = [dictionary3 allKeys];

        for(NSString *key in allKeys1)

        {

            NSString *str = [dictionary3 objectForKey:key];

            NSLog(@"%@=%@",key,str);

        }

2.可变字典

2.1可变字典的创建与使用

        NSDictionary *dic = @{@"name":@"xiaoming",@"age":@""};

        NSDictionary *dic1 = @{@"age":@"",@"score":@""};

        NSMutableDictionary *muDic = [[NSMutableDictionary alloc] init];

        //从一个字典内添加元素到可变字典

        //注意:

        //当dic与可变字典有相同的key时,不添加这个key，但是会将key对应的value覆盖。

        [muDic addEntriesFromDictionary:dic];

        NSLog(@"%@",muDic);

        [muDic addEntriesFromDictionary:dic1];

        NSLog(@"%@",muDic);

        //添加一个元素

        //注意:

        //1，setObject:forKey:  当key不存在时就是添加元素，当key存在时就是修改元素值

        [muDic setObject:@"mingming" forKey:@"nickname"];

        [muDic setObject:@"xiaohua" forKey:@"name"];

        NSLog(@"%@",muDic);

        //删除一个元素

        [muDic removeObjectForKey:@"name"];

        NSLog(@"%@",muDic);

        //删除一个keys数组里面对应的所有元素

        [muDic removeObjectsForKeys:@[@"nickname",@"aaa"]];

        NSLog(@"%@",muDic);

        //删除字典内的所有元素

        [muDic removeAllObjects];

        NSLog(@"%@",muDic);

        //修改字典

        [muDic setDictionary:dic];

        NSLog(@"%@",muDic);