在Objective-C中有没有(stringByAppendingString:)字符串连接的快捷方式,或者一般使用NSString的快捷方式?

例如,我想做:

NSString *myString = @"This";
NSString *test = [myString stringByAppendingString:@" is just a test"];

更像是:

string myString = "This";
string test = myString + " is just a test";

当前回答

对于所有Objective C爱好者,在ui测试中需要这个:

-(void) clearTextField:(XCUIElement*) textField{

    NSString* currentInput = (NSString*) textField.value;
    NSMutableString* deleteString = [NSMutableString new];

    for(int i = 0; i < currentInput.length; ++i) {
        [deleteString appendString: [NSString stringWithFormat:@"%c", 8]];
    }
    [textField typeText:deleteString];
}

其他回答

如果你有两个NSString字面量,你也可以这样做:

NSString *joinedFromLiterals = @"ONE " @"MILLION " @"YEARS " @"DUNGEON!!!";

这对于加入#定义也很有用:

#define STRINGA @"Also, I don't know "
#define STRINGB @"where food comes from."
#define JOINED STRINGA STRINGB

享受。

这是为了更好的日志记录,而且仅仅是日志记录——基于dicius优秀的多参数方法。我定义了一个Logger类,并像这样调用它:

[Logger log: @"foobar ", @" asdads ", theString, nil];

几乎很好,除了var args必须以“nil”结束,但我想在Objective-C中没有办法绕过它。

Logger.h

@interface Logger : NSObject {
}
+ (void) log: (id) first, ...;
@end

Logger.m

@implementation Logger

+ (void) log: (id) first, ...
{
    // TODO: make efficient; handle arguments other than strings
    // thanks to @diciu http://stackoverflow.com/questions/510269/how-do-i-concatenate-strings-in-objective-c
    NSString * result = @"";
    id eachArg;
    va_list alist;
    if(first)
    {
        result = [result stringByAppendingString:first];
        va_start(alist, first);
        while (eachArg = va_arg(alist, id)) 
        {
            result = [result stringByAppendingString:eachArg];
        }
        va_end(alist);
    }
    NSLog(@"%@", result);
}

@end 

为了只连接字符串,我在NSString上定义了一个Category,并添加了一个静态(+)连接方法,它看起来完全像上面的log方法,除了它返回字符串。它在NSString上,因为它是一个字符串方法,它是静态的,因为你想从1-N个字符串中创建一个新字符串,而不是在任何一个作为append一部分的字符串上调用它。

NSString *label1 = @"Process Name: ";
NSString *label2 = @"Process Id: ";
NSString *processName = [[NSProcessInfo processInfo] processName];
NSString *processID = [NSString stringWithFormat:@"%d", [[NSProcessInfo processInfo] processIdentifier]];
NSString *testConcat = [NSString stringWithFormat:@"%@ %@ %@ %@", label1, processName, label2, processID];

当我测试时,这两种格式都可以在XCode7中工作:

NSString *sTest1 = {@"This" " and that" " and one more"};
NSString *sTest2 = {
  @"This"
  " and that"
  " and one more"
};

NSLog(@"\n%@\n\n%@",sTest1,sTest2);

出于某种原因,您只需要在混合的第一个字符串上使用@操作符。

但是,它不能用于变量插入。为此,您可以使用这个极其简单的解决方案,除了对“cat”而不是“and”使用宏。

这样使用stringByAppendingString:

NSString *string1, *string2, *result;

string1 = @"This is ";
string2 = @"my string.";

result = [result stringByAppendingString:string1];
result = [result stringByAppendingString:string2];

OR

result = [result stringByAppendingString:@"This is "];
result = [result stringByAppendingString:@"my string."];