對數(shù)組的操作：遍歷、篩選、映射、替換
1、遍歷

NSArray * array = @[@"",@"",@""];
[array.rac_sequence.signal subscribeNext:^(id  _Nullable x) {
    NSLog(@"數(shù)組內(nèi)容：%@", x);
 }];

2、篩選

NSArray *filter = [[array.rac_sequence filter:^BOOL(id value) {
    return  [value integerValue] > 0 ;
 }] array];
 NSLog(@"filter:%@",filter); 

3、映射

NSArray *map = [[array.rac_sequence map:^id(id value) {
    NSInteger a = [value integerValue] * [value integerValue];
    return [NSString stringWithFormat:@"%ld", a];
 }] array];

4、替換

NSArray * array1 = @[@"1",@"2",@"3"];
NSArray * newArray = [[array1.rac_sequence mapReplace:@"88"] array];