構建可變數量的鍵和格式的字符串

Question

我有一個包含我的數據的NSDictionary對象。我傳入一組鍵名和顯示格式來表示我的數據的字符串。

[self displayMyDataWithTheseKeys:myKeyArray inThisFormat:myFormat]; 

，其中，例如，

myKeyArray = [NSArray arrayWithObjects: @"Key1", @"Key2", nil]; 

myFormat = [NSString stringWithString: @"%@ to the %@ degree"]; 

然而，myFormat可能改變，並且鍵的陣列中的數目也可以變化。

如果數組中元素的數量總是2，那麼這將是微不足道的。但是，如何處理可變數量的元素？

Answer 1

這裏沒有真正的內置方法，但它相對比較容易解析格式字符串與NSScanner。這裏有一個簡單的例子，它只能處理%@格式說明，但作爲一個NSArray所有元素都是對象，而不是原始類型，無論如何，這一問題並不應該：

NSArray *myKeyArray = [NSArray arrayWithObjects: @"Key1", @"Key2", nil]; 
NSString *myFormat = [NSString stringWithString: @"%@ to the %@ degree"]; 

NSMutableString *result = [NSMutableString string]; 
NSScanner *scanner = [NSScanner scannerWithString:myFormat]; 
[scanner setCharactersToBeSkipped:[NSCharacterSet illegalCharacterSet]]; 
int i = 0; 
while (![scanner isAtEnd]) { 
    BOOL scanned = [scanner scanString:@"%@" intoString:NULL]; 
    if (scanned) { 
     if (i < [myKeyArray count]) { 
      [result appendString:[myKeyArray objectAtIndex:i]]; 
      i++; 
     } else { 
      //Handle error: Number of format specifiers doesn't 
      //match number of keys in array... 
     } 
    } 
    NSString *chunk = nil; 
    [scanner scanUpToString:@"%@" intoString:&chunk]; 
    if (chunk) { 
     [result appendString:chunk]; 
    } 
} 

Answer 2

用途：stringByAppendingString

下面是關於如何使用它的一個例子：

NSString *someString = @"String"; 

someString = [someString stringByAppendingString:[NSString stringWithFormat:@"%@",variable1]]; 
someString = [someString stringByAppendingString:[NSString stringWithFormat:@"%@",variable2]]; 
someString = [someString stringByAppendingString:[NSString stringWithFormat:@"%@",variable3]]; 

...等等

如果你有，你希望把鍵數組一個字符串：

NSString *string = @"And the keys are:\n"; 

    for(int i = 0; i < [array count]; i++) 
    { 
     NSString *thisKey = (NSString *)[array objectAtIndex:i]; 

     string = [string stringByAppendingString:[NSString stringWithFormat:@"Key number %d is %@",i,thisKey]]; 
    }