NSArray 的前三项转换为 NSString？

Question

将数组的前三个对象（或者 1 或 2，如果数组有多大）转换为以逗号分隔的字符串的最有效方法是什么。我有一种感觉，有一种方法可以用块来实现，但我无法解决。

对象是 Bands，存储在 bandArray 中，每个 band 的属性包括 bandName。

所以输出会是这样的

String
"Abba"                    <- when there is one object
"Abba, Kiss"              <- when there is two objects
"Abba, Kiss, Nirvana"     <- when there is three objects
"Abba, Kiss, Nirvana"     <- when there is four objects. after three, names are ignored

Answer 1

您可以使用 subarrayWithRange: 来实现：

NSString *res = [[[theArray subarrayWithRange:NSMakeRange(0, fmin(3, [theArray count]))] 
                  valueForKey:@"brandName"] 
                 componentsJoinedByString:@", "];

Answer 2

NSUInteger count = [bandArray count];
if (count > 3){
    count = 3;
}
NSString * resultString = [[bandArray subarrayWithRange:NSMakeRange(0,count)]  componentsJoinedByString:@", "];

Answer 3

您可以尝试以下操作（尽管它完全未经测试，因为我远离我的 Mac）

int bandCount = 1;
NSString *bands;
for (NSString *band in bandArray) {
    if (bandCount > 3) break;
    if (bandCount == 1) {
        bands = [NSString stringWithFormat:@"%@", band];
    } else {        
        bands = [NSString stringWithFormat:@"%@, %@", bands, band];
    }
    bandCount ++;
}

Answer 4

可能不是最快的，但却是最简单的，谁知道苹果苹果在创建子数组时可能会做一些聪明的事情。

[[array subarrayWithRange:NSMakeRange(0,MIN(array.length,3)] componentsJoinedByString:@","];