取出字符串中的指定内容
- (NSString *)CopyPartTextToString : (NSString *)SourceData FirstPlaceIndex : (NSInteger) FirstPlaceIndexLastPlaceIndex : (NSInteger) LastPlaceIndex {if (FirstPlaceIndex < 1) FirstPlaceIndex = 1;if (LastPlaceIndex > [SourceData length]) LastPlaceIndex = [SourceData length];if (FirstPlaceIndex > LastPlaceIndex) return nil;NSRange range;range.location = FirstPlaceIndex - 1;range.length = LastPlaceIndex - FirstPlaceIndex + 1;return [SourceData substringWithRange:range];}?