stringWithFormat中的多个参数:“n $”位置说明符 [英] Multiple arguments in stringWithFormat: “n$” positional specifiers
问题描述
在我们当前的实现中,我们想要更改我们的字符串参数(推送通知loc-args)并添加新参数。但我们希望旧版本的用户仍然使用参数#3,而对于新用户,我们希望使用参数#4。所以在我们的新实现中,我们有以下代码:
In our current implementation we want to change our string arguments (Push notification loc-args) and add new arguments. But we want user's of our old Versions to still use argument #3 and for new user's we want to user argument #4. So in our new implementation we have following code :
NSString *format = @"%2$@, %1$@ ,%4$@";
NSArray *arg = @[@"Argument 1", @"Argument 2",@"Argument 3",@"Argument 4"];
NSString *ouptput = [NSString stringWithFormat:format, arg[0], arg[1], arg[2], arg[3]];
OutPut:参数2,参数1,参数3
OutPut: Argument 2, Argument 1 ,Argument 3
我们预期它是
参数2,参数1,参数4
Argument 2, Argument 1 ,Argument 4
我们如何实现 Argument 4
。 stringWithFormat的任何其他选择:
注意:Apple锁定屏幕推送通知是正确的(参数2,参数1,参数4
)但是 stringWithFormat:
没有那样处理
Note: Apple lock screen push notification is correct (Argument 2, Argument 1 ,Argument 4
) but stringWithFormat:
not handles it that way
推荐答案
我实现了一个自定义方法来实现预期的输出。此方法可以处理缺少的位置说明符。此方法仅适用于包含位置说明符%n $ @
的格式。
I implemented a custom method to achieve expected output. This method can handle missing positional specifier. This method will only work for format containing positional specifier %n$@
.
/**
@param format String format with positional specifier
@param arg Array of arguments to replace positional specifier in format
@return Formatted output string
*/
+(NSString*)stringWithPositionalSpecifierFormat:(NSString*)format arguments:(NSArray*)arg
{
static NSString *pattern = @"%\\d\\$@";
NSError *error;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:NSRegularExpressionCaseInsensitive error:&error];
NSMutableString *mString = [[NSMutableString alloc] initWithString:format];
NSArray *allMatches = [regex matchesInString:format options:0 range:NSMakeRange(0, [format length])];
if (!error && allMatches>0)
{
for (NSTextCheckingResult *aMatch in allMatches)
{
NSRange matchRange = [aMatch range];
NSString *argPlaceholder = [format substringWithRange:matchRange];
NSMutableString *position = [argPlaceholder mutableCopy];
[position replaceOccurrencesOfString:@"%" withString:@"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [position length])];
[position replaceOccurrencesOfString:@"$@" withString:@"" options:NSCaseInsensitiveSearch range:NSMakeRange(0, [position length])];
int index = position.intValue;
//Replace with argument
[mString replaceOccurrencesOfString:argPlaceholder withString:arg[index-1] options:NSCaseInsensitiveSearch range:NSMakeRange(0, [mString length])];
}
}
return mString;
}
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