字符串与数组相互转化

NSArray * ary = @[@1,@3];
1、先把数组转换成字符串

NSString *string = [ary componentsJoinedByString:@","];//,为分隔符

2、再把字符串转换成数组，即可把整形数组转换成字符串数组

ary = [string componentsSeparatedByString:@","];