[OC Foundation框架

A.NSSet

跟NSArray一样，不可变

NSArray 自然顺序

NSSet是无序的

NSSet不允许存入重复元素，可以用来过滤重复元素

 

也有可变的NSMutableSet

 

B.集合转换

       

 // 1.NSArray 转换成 NSMutableArray
        NSArray *array = @[@"one", @"two", @"three"];
        NSMutableArray *muArray = [NSMutableArrayarrayWithArray:array];
        NSLog(@"muArray = %@", muArray);
       
       
        // 2.NSDictionary 转换成 NSMutableDictionary
        NSDictionary *dic = @{@"one":@"1", @"two":@"2", @"three":@"3"};
        NSMutableDictionary *muDic = [NSMutableDictionarydictionaryWithDictionary:dic];
        NSLog(@"muDic = %@", muDic);
       
        // 3.NSArray -> NSSet -> NSMutableSet
        NSSet *set = [NSSetsetWithArray:array];
        NSMutableSet *muSet = [NSMutableSetsetWithSet:set];
        NSLog(@"muSet = %@", muSet);
       
        // 4.NSDcitionary -> NSArray
        NSArray *allKeys = [dic allKeys];
        NSLog(@"allKeys = %@", allKeys);
        NSArray *allValues = [dic allValues];
        NSLog(@"allValues = %@", allValues);
       
        // 5.NSString -> NSArray
        NSString *str = @"www.baidu.com";
        NSArray *array2 = [str componentsSeparatedByString:@"."];
        NSLog(@"array2 = %@", array2);