Objective-C 中连接 NSString 的快捷方式
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Shortcuts in Objective-C to concatenate NSStrings
提问by typeoneerror
Are there any shortcuts to (stringByAppendingString:) string concatenation in Objective-C, or shortcuts for working with NSStringin general?
stringByAppendingString:在 Objective-C 中是否有 ( ) 字符串连接的快捷方式，或者NSString一般使用的快捷方式？
For example, I'd like to make:
例如，我想做：
NSString *myString = @"This";
NSString *test = [myString stringByAppendingString:@" is just a test"];
something more like:
更像是：
string myString = "This";
string test = myString + " is just a test";
采纳答案by Chris Blackwell
Two answers I can think of... neither is particularly as pleasant as just having a concatenation operator.
我能想到的两个答案......都不像只有一个串联运算符那么令人愉快。
First, use an NSMutableString, which has an appendStringmethod, removing some of the need for extra temp strings.
首先，使用一个NSMutableString，它有一个appendString方法，消除了对额外临时字符串的一些需要。
Second, use an NSArrayto concatenate via the componentsJoinedByStringmethod.
其次，使用 anNSArray通过componentsJoinedByString方法进行连接。
回答by diciu
An option:
一个选项：
[NSString stringWithFormat:@"%@/%@/%@", one, two, three];
Another option:
另外一个选项：
I'm guessing you're not happy with multiple appends (a+b+c+d), in which case you could do:
我猜你对多个附加（a+b+c+d）不满意，在这种情况下你可以这样做：
NSLog(@"%@", [Util append:one, @" ", two, nil]); // "one two"
NSLog(@"%@", [Util append:three, @"/", two, @"/", one, nil]); // three/two/one
using something like
使用类似的东西
+ (NSString *) append:(id) first, ...
{
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);
}
return result;
}
回答by Johannes Fahrenkrug
If you have 2 NSString literals, you can also just do this:
如果您有 2 个 NSString文字，您也可以这样做：
NSString *joinedFromLiterals = @"ONE " @"MILLION " @"YEARS " @"DUNGEON!!!";
That's also useful for joining #defines:
这对于加入#defines 也很有用：
#define STRINGA @"Also, I don't know "
#define STRINGB @"where food comes from."
#define JOINED STRINGA STRINGB
Enjoy.
享受。
回答by Kyle Clegg
I keep returning to this post and always end up sorting through the answers to find this simple solution that works with as many variables as needed:
我一直回到这篇文章，最终总是对答案进行排序，以找到这个简单的解决方案，该解决方案可以根据需要处理尽可能多的变量：
[NSString stringWithFormat:@"%@/%@/%@", three, two, one];
For example:
例如：
NSString *urlForHttpGet = [NSString stringWithFormat:@"http://example.com/login/username/%@/userid/%i", userName, userId];
回答by Sidd Menon
Create a method:
创建一个方法：
- (NSString *)strCat: (NSString *)one: (NSString *)two
{
NSString *myString;
myString = [NSString stringWithFormat:@"%@%@", one , two];
return myString;
}
Then, in whatever function you need it in, set your string or text field or whatever to the return value of this function.
然后，在您需要它的任何函数中，将字符串或文本字段或任何内容设置为该函数的返回值。
Or, to make a shortcut, convert the NSString into a C++ string and use the '+' there.
或者，要创建快捷方式，请将 NSString 转换为 C++ 字符串并在那里使用“+”。
回答by Palimondo
Well, as colon is kind of special symbol, but ispart of method signature, it is possible to exted the NSStringwith category to add this non-idiomaticstyle of string concatenation:
那么，结肠癌是一种特殊的符号，但是是方法签名的一部分，有可能加长的NSString类别为添加这个非惯用的字符串连接的风格：
[@"This " : @"feels " : @"almost like " : @"concatenation with operators"];
You can define as many colon separated arguments as you find useful... ;-)
您可以定义尽可能多的以冒号分隔的参数... ;-)
For a good measure, I've also added concat:with variable arguments that takes nilterminated list of strings.
作为一个很好的衡量标准，我还添加了concat:带有nil终止字符串列表的变量参数。
// NSString+Concatenation.h
#import <Foundation/Foundation.h>
@interface NSString (Concatenation)
- (NSString *):(NSString *)a;
- (NSString *):(NSString *)a :(NSString *)b;
- (NSString *):(NSString *)a :(NSString *)b :(NSString *)c;
- (NSString *):(NSString *)a :(NSString *)b :(NSString *)c :(NSString *)d;
- (NSString *)concat:(NSString *)strings, ...;
@end
// NSString+Concatenation.m
#import "NSString+Concatenation.h"
@implementation NSString (Concatenation)
- (NSString *):(NSString *)a { return [self stringByAppendingString:a];}
- (NSString *):(NSString *)a :(NSString *)b { return [[self:a]:b];}
- (NSString *):(NSString *)a :(NSString *)b :(NSString *)c
{ return [[[self:a]:b]:c]; }
- (NSString *):(NSString *)a :(NSString *)b :(NSString *)c :(NSString *)d
{ return [[[[self:a]:b]:c]:d];}
- (NSString *)concat:(NSString *)strings, ...
{
va_list args;
va_start(args, strings);
NSString *s;
NSString *con = [self stringByAppendingString:strings];
while((s = va_arg(args, NSString *)))
con = [con stringByAppendingString:s];
va_end(args);
return con;
}
@end
// NSString+ConcatenationTest.h
#import <SenTestingKit/SenTestingKit.h>
#import "NSString+Concatenation.h"
@interface NSString_ConcatenationTest : SenTestCase
@end
// NSString+ConcatenationTest.m
#import "NSString+ConcatenationTest.h"
@implementation NSString_ConcatenationTest
- (void)testSimpleConcatenation
{
STAssertEqualObjects([@"a":@"b"], @"ab", nil);
STAssertEqualObjects([@"a":@"b":@"c"], @"abc", nil);
STAssertEqualObjects([@"a":@"b":@"c":@"d"], @"abcd", nil);
STAssertEqualObjects([@"a":@"b":@"c":@"d":@"e"], @"abcde", nil);
STAssertEqualObjects([@"this " : @"is " : @"string " : @"concatenation"],
@"this is string concatenation", nil);
}
- (void)testVarArgConcatenation
{
NSString *concatenation = [@"a" concat:@"b", nil];
STAssertEqualObjects(concatenation, @"ab", nil);
concatenation = [concatenation concat:@"c", @"d", concatenation, nil];
STAssertEqualObjects(concatenation, @"abcdab", nil);
}
回答by Taimur Ajmal
Use stringByAppendingString:this way:
使用stringByAppendingString:这种方式：
NSString *string1, *string2, *result;
string1 = @"This is ";
string2 = @"my string.";
result = [result stringByAppendingString:string1];
result = [result stringByAppendingString:string2];
OR
或者
result = [result stringByAppendingString:@"This is "];
result = [result stringByAppendingString:@"my string."];
回答by EthanB
Macro:
宏：
// stringConcat(...)
// A shortcut for concatenating strings (or objects' string representations).
// Input: Any number of non-nil NSObjects.
// Output: All arguments concatenated together into a single NSString.
#define stringConcat(...) \
[@[__VA_ARGS__] componentsJoinedByString:@""]
Test Cases:
测试用例：
- (void)testStringConcat {
NSString *actual;
actual = stringConcat(); //might not make sense, but it's still a valid expression.
STAssertEqualObjects(@"", actual, @"stringConcat");
actual = stringConcat(@"A");
STAssertEqualObjects(@"A", actual, @"stringConcat");
actual = stringConcat(@"A", @"B");
STAssertEqualObjects(@"AB", actual, @"stringConcat");
actual = stringConcat(@"A", @"B", @"C");
STAssertEqualObjects(@"ABC", actual, @"stringConcat");
// works on all NSObjects (not just strings):
actual = stringConcat(@1, @" ", @2, @" ", @3);
STAssertEqualObjects(@"1 2 3", actual, @"stringConcat");
}
Alternate macro:(if you wanted to enforce a minimum number of arguments)
替代宏：（如果您想强制执行最少数量的参数）
// stringConcat(...)
// A shortcut for concatenating strings (or objects' string representations).
// Input: Two or more non-nil NSObjects.
// Output: All arguments concatenated together into a single NSString.
#define stringConcat(str1, str2, ...) \
[@[ str1, str2, ##__VA_ARGS__] componentsJoinedByString:@""];
回答by FreeAsInBeer
When building requests for web services, I find doing something like the following is very easy and makes concatenation readable in Xcode:
在构建 Web 服务请求时，我发现执行以下操作非常简单，并且可以在 Xcode 中读取连接：
NSString* postBody = {
@"<?xml version=\"1.0\" encoding=\"utf-8\"?>"
@"<soap:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap=\"http://schemas.xmlsoap.org/soap/envelope/\">"
@" <soap:Body>"
@" <WebServiceMethod xmlns=\"\">"
@" <parameter>test</parameter>"
@" </WebServiceMethod>"
@" </soap:Body>"
@"</soap:Envelope>"
};
回答by FreeAsInBeer
Shortcut by creating AppendString (AS) macro ...
通过创建 AppendString (AS) 宏的快捷方式...
#define AS(A,B) [(A) stringByAppendingString:(B)]
NSString *myString = @"This"; NSString *test = AS(myString,@" is just a test");
Note:
笔记：
If using a macro, of course just do it with variadic arguments, see EthanB's answer.
如果使用宏，当然只需使用可变参数即可，请参阅 EthanB 的答案。
