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
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."];
NSNumber *lat = [NSNumber numberWithDouble:destinationMapView.camera.target.latitude];
NSNumber *lon = [NSNumber numberWithDouble:destinationMapView.camera.target.longitude];
NSString *DesconCatenated = [NSString stringWithFormat:@"%@|%@",lat,lon];
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];
我喜欢的方法是:
NSString *firstString = @"foo";
NSString *secondString = @"bar";
NSString *thirdString = @"baz";
NSString *joinedString = [@[firstString, secondString, thirdString] join];
你可以通过在NSArray中添加join方法来实现:
#import "NSArray+Join.h"
@implementation NSArray (Join)
-(NSString *)join
{
return [self componentsJoinedByString:@""];
}
@end
@[]是NSArray的简短定义，我认为这是连接字符串最快的方法。
如果你不想使用类别，直接使用componentsJoinedByString:方法:
NSString *joinedString = [@[firstString, secondString, thirdString] componentsJoinedByString:@""];
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。
