如何将零个字符串列表传递给Objective-C函数? [英] How do I pass a nil-terminted list of strings to an Objective-C function?
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问题描述
函数[NSArray arrayWithObjects:foo,bar,nil]将以nil终止的字符串列表传递给函数.
The function [NSArray arrayWithObjects:foo, bar, nil] passes a nil-terminted list of string to a function.
如果我想编写类似的函数,则声明是什么样的,以及如何遍历字符串?
If I want to write a similar function, what does the declaration look like, and how do I iterate through the strings?
推荐答案
I quote http://developer.apple.com/mac/library/qa/qa2005/qa1405.html, which contains the full truth.
这是一个Objective-C类别的示例,其中包含一个追加了可变参数的方法 NSMutableArray实例的自变量以零结尾的列表中的所有对象:
Here's an example of an Objective-C category, containing a variadic method that appends all the objects in a nil-terminated list of arguments to an NSMutableArray instance:
#import <Cocoa/Cocoa.h>
@interface NSMutableArray (variadicMethodExample)
- (void) appendObjects:(id) firstObject, ...; // This method takes a nil-terminated list of objects.
@end
@implementation NSMutableArray (variadicMethodExample)
- (void) appendObjects:(id) firstObject, ...
{
id eachObject;
va_list argumentList;
if (firstObject) // The first argument isn't part of the varargs list,
{ // so we'll handle it separately.
[self addObject: firstObject];
va_start(argumentList, firstObject); // Start scanning for arguments after firstObject.
while (eachObject = va_arg(argumentList, id)) // As many times as we can get an argument of type "id"
[self addObject: eachObject]; // that isn't nil, add it to self's contents.
va_end(argumentList);
}
}
@end
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