The function [NSArray arrayWithObjects:foo, bar, nil] passes a nil-terminted list of string to a function.
函数[NSArray arrayWithObjects:foo, bar, nil]将一个带nil端点的字符串列表传递给函数。
If I want to write a similar function, what does the declaration look like, and how do I iterate through the strings?
如果我想编写一个类似的函数,那么声明是什么样子的,我如何遍历字符串呢?
3 个解决方案
#1
9
I quote http://developer.apple.com/mac/library/qa/qa2005/qa1405.html, which contains the full truth.
我引用了http://developer.apple.com/mac/library/qa/qa2005/qa1405.html,它包含了全部的真理。
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:
这里有一个Objective-C类别的例子,它包含一个变量方法,它将nil终止的参数列表中的所有对象附加到一个NSMutableArray实例中:
#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
#2
0
I'm not sure if Obj-c has its own particular support for this, but in C you do:
我不确定object - C是否有它自己的特别支持,但是在C中你有:
function nArgs(int n, ...)
To support multiple args, and the following style of implementation:
支持多种args,实现方式如下:
{
va_list ap;
va_start(ap, n);
while (n-- > 0) {
int i = va_arg(ap, int);
}
va_end(ap);
}
Here for more info: http://www.cprogramming.com/tutorial/lesson17.html
这里有更多的信息:http://www.cprogramming.com/tutorial/lesson17.html。
#3
0
NSArray declares that method like this:
NSArray这样宣布这个方法:
+ (id)arrayWithObjects:(id)firstObj, ... NS_REQUIRES_NIL_TERMINATION;
When you implement it, you'll need to use the va_arg macros to get at each argument.
实现它时,需要使用va_arg宏来获取每个参数。
Look up va_list
, va_start()
, va_arg()
, etc.
查找va_list、va_start()、va_arg()等。
More info can be seen in the man page for va_arg
and by looking at stdarg.h
在va_arg的手册页和查看stdarg.h可以看到更多信息
#1
9
I quote http://developer.apple.com/mac/library/qa/qa2005/qa1405.html, which contains the full truth.
我引用了http://developer.apple.com/mac/library/qa/qa2005/qa1405.html,它包含了全部的真理。
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:
这里有一个Objective-C类别的例子,它包含一个变量方法,它将nil终止的参数列表中的所有对象附加到一个NSMutableArray实例中:
#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
#2
0
I'm not sure if Obj-c has its own particular support for this, but in C you do:
我不确定object - C是否有它自己的特别支持,但是在C中你有:
function nArgs(int n, ...)
To support multiple args, and the following style of implementation:
支持多种args,实现方式如下:
{
va_list ap;
va_start(ap, n);
while (n-- > 0) {
int i = va_arg(ap, int);
}
va_end(ap);
}
Here for more info: http://www.cprogramming.com/tutorial/lesson17.html
这里有更多的信息:http://www.cprogramming.com/tutorial/lesson17.html。
#3
0
NSArray declares that method like this:
NSArray这样宣布这个方法:
+ (id)arrayWithObjects:(id)firstObj, ... NS_REQUIRES_NIL_TERMINATION;
When you implement it, you'll need to use the va_arg macros to get at each argument.
实现它时,需要使用va_arg宏来获取每个参数。
Look up va_list
, va_start()
, va_arg()
, etc.
查找va_list、va_start()、va_arg()等。
More info can be seen in the man page for va_arg
and by looking at stdarg.h
在va_arg的手册页和查看stdarg.h可以看到更多信息