在 NSString 中动态追加和删除子字符串

Question

我正在从NSString动态附加和删除子字符串 -

在我附加的特定操作中（我在添加新字符串时使用逗号分隔符）-

self.selectedString = [self.selectedString length] < 1 ? newSelectedString 
                                                       : [self.selectedString stringByAppendingFormat:@",%@",newSelectedString];

删除-现在，在删除字符串时，这个逗号给我带来了问题。目前我正在使用一种解决方案，因为 -

self.selectedString = [self.selectedString stringByReplacingOccurrencesOfString:newSelectedString
                                                                     withString:@""];
NSRange rangeSingleComma = [self.selectedString rangeOfString:@","];
NSRange rangeDoubleComma = [self.selectedString rangeOfString:@",,"];
if (rangeSingleComma.location == [self.selectedString length] - 1) {
    self.selectedString = [self.selectedString substringToIndex:[self.selectedString length] - 1];
}
if (rangeSingleComma.location == 0) {
    self.selectedString = [self.selectedString substringFromIndex:1];
}
if (rangeDoubleComma.location != NSNotFound) {
    self.selectedString = [self.selectedString stringByReplacingOccurrencesOfString:@",,"
                                                                         withString:@","];
 }

但这是一个非常肮脏的方法，任何人都可以为此提出一个好方法吗？

Answer 1

你可以做这样的事情

NSString *str = @"aaa,bbb,ccc";
NSMutableArray *arr = [[str componentsSeparatedByString:@","] mutableCopy];
int indexToRemove = -1;
for (int i = 0; i < arr.count; i++) {
    NSString *string = [arr objectAtIndex:i];
    if([string isEqualToString:@"aaa"])
    {
        indexToRemove = i;
        break;
    }
}
if(indexToRemove != -1)
{
    [arr removeObjectAtIndex:indexToRemove];
}
NSString *newString = [arr componentsJoinedByString:@","];

Answer 2

您需要将此逗号分隔的列表存储为字符串吗？相反，尝试维护NSString的NSArray/NSMutableArray。这使得随意添加或删除任何项目变得容易。当您需要数组的逗号分隔字符串表示形式时，只需执行以下操作：

 [self.selectedArray componentsJoinedByString:@","]

如果您仍想使用 self.selectedString 属性，只需将上面的代码行放在 getter 方法中：

 - (NSString *) selectedString {
      return [self.selectedArray componentsJoinedByString:@","]
 }