blocks|key|1293935|text|这没有区别，但是您应该知道，只有第一个“标记”(所谓的“标记”)定义了类型名称，而*不是类型名称的一部分。也就是说：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1293936|NSString+*aString,+bString;|code-block|syntax|javascript|1293937|创建一个指向NSString的指针和一个NSString。要使两者都成为指针，请执行以下任一操作：|offset|length|style|CODE|1293938|NSString+*aString,+*bString;|1293939|或者：|1293940|NSString+*aString;
NSString+*bString;|1293941|entityMap^0|0|0|6|8|K|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|12|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|T|$]]

There is no difference, however you should be aware that only the first "token" (so to speak) defines the type name, and the * is not part of the type name. That is to say:

<pre><code>NSString *aString, bString;
</code></pre>

Creates one pointer-to-<code>NSString</code>, and one <code>NSString</code>. To get both to be pointers, do either:

<pre><code>NSString *aString, *bString;
</code></pre>

or:

<pre><code>NSString *aString;
NSString *bString;
</code></pre>

blocks|key|1293538|text|1.++NSString+*string;
2.++NSString+*+string;
3.++(NSString+*)+string;
4.++NSString*+string;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1293539|1、2和4完全相同。这都是风格。你可以随心所欲地挑选，或者把它们混在一起。|unstyled|1293540|选择#3还有另一个含义，它用于铸造。例如：|1293541|t+=+(NSString+*)string+;|1293542|会将string强制转换为NSString指针。|offset|length|style|CODE|1293543|但选择#3是您可能会在.h文件或.m文件的函数定义中使用的语法。在一个实际的函数中，在"run“的代码中，它有不同的含义。|1293544|entityMap^0|0|0|0|0|2|6|D|8|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|V|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|A|$B|C]]|$1|K|3|L|5|F|7|Y|8|@$M|Z|N|10|O|P]|$M|11|N|12|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|F|7|13|8|@]|9|@]|A|$]]|$1|S|3|-4|5|F|7|14|8|@]|9|@]|A|$]]]|T|$]]

<pre><code>1. NSString *string;
2. NSString * string;
3. (NSString *) string;
4. NSString* string;
</code></pre>

1, 2 and 4 are exactly identical. It's all style. Pick whatever you want, or mix it up.

Choice #3 has another meaning also, it's used in casting. For example:

<pre><code>t = (NSString *)string ;
</code></pre>

will cast <code>string</code> to an <code>NSString</code> pointer. 

But choice #3 is the syntax you'd probably use in a .h file or in the function definition in a .m file. Inside an actual function, in code which is "run" it has a different meaning.

blocks|key|1293474|text|没有区别--这是风格的问题。它们都声明了一个名为string的变量，这是一个指向NSString的指针。在某些上下文(特别是方法声明)中，括号是必需的，以便澄清它是一个类型声明。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1293475|entityMap^0|O|6|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

There is no difference — it's a matter of style. They all declare a variable called <code>string</code> that's a pointer to an NSString. The parentheses are necessary in some contexts (particularly method declarations) in order to clarify that it's a type declaration.

blocks|key|1508386|text|1.++NSString+*string;
2.++NSString+*+string;
3.++(NSString+*)+string;
4.++NSString*+string;|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1508387|1、2和4是等价的。C语言(以及C的Objective-C超集)指定了一种对空格不敏感的语法。因此，您可以根据风格随意添加空格。所有相关语法均由非空格字符(例如{、}、;等)分隔1。|unstyled|offset|length|style|CODE|1508388|3要么是类型转换(告诉C编译器使用NSString*类型，而不管声明的string类型是什么。在Objective-C中，很少需要对对象实例进行类型转换。可以对可以引用任何对象类型的实例的变量使用id类型。|1508389|在方法声明中，语法3(有时没有结束分号)用于声明方法参数的类型。Objective-C方法可能如下所示：|1508390|-+(void)myMethodThatTakesAString:(NSString*)string;|1508391|在此声明中，名为string的参数的类型是NSString*类型(前导的-表示实例方法，而不是类方法)。具有多个参数的方法声明可能如下所示：|1508392|-+(void)myMethodTakingAString:(NSString*)string+andAnInteger:(NSInteger)intParam;|1508393|1这与Python等使用空格作为块分隔符的语言进行了比较。|1508394|entityMap^0|0|28|1|2A|1|2C|1|0|H|9|Z|6|2Q|2|0|0|0|8|6|L|9|10|1|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|Z|8|@$G|10|H|11|I|J]|$G|12|H|13|I|J]|$G|14|H|15|I|J]]|9|@]|A|$]]|$1|K|3|L|5|F|7|16|8|@$G|17|H|18|I|J]|$G|19|H|1A|I|J]|$G|1B|H|1C|I|J]]|9|@]|A|$]]|$1|M|3|N|5|F|7|1D|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1E|8|@]|9|@]|A|$B|C]]|$1|Q|3|R|5|F|7|1F|8|@$G|1G|H|1H|I|J]|$G|1I|H|1J|I|J]|$G|1K|H|1L|I|J]]|9|@]|A|$]]|$1|S|3|T|5|6|7|1M|8|@]|9|@]|A|$B|C]]|$1|U|3|V|5|F|7|1N|8|@]|9|@]|A|$]]|$1|W|3|-4|5|F|7|1O|8|@]|9|@]|A|$]]]|X|$]]

<pre><code>1. NSString *string;
2. NSString * string;
3. (NSString *) string;
4. NSString* string;
</code></pre>

1,2 and 4 are equivalent. The C language (and the Objective-C superset of C) specify a syntax that is insensitive to white space. So you can freely add spaces where you choose as a matter of style. All relevant syntax is delimited by non-whitespace characters (e.g. <code>{</code>, <code>}</code>, <code>;</code>, etc.) [1].

3 is either a type cast (telling the C compiler to use the <code>NSString*</code> type regardless of the declared type of <code>string</code>. In Objective-C, type casting of object instances is rarely necessary. You can use the <code>id</code> type for variables that can reference instances of any object type.

In method declarations, syntax 3 (sometimes without the ending semicolon) is used to declare the type of method parameters. An Objective-C method may look like this:

<pre><code>- (void)myMethodThatTakesAString:(NSString*)string;
</code></pre>

In this declaration, the type of the argument named <code>string</code> is type <code>NSString*</code> (the leading <code>-</code> indicates an instance method as oppose to a class method). A method declaration with more than one parameter might look like this:

<pre><code>- (void)myMethodTakingAString:(NSString*)string andAnInteger:(NSInteger)intParam;
</code></pre>

[1] This is compared to languages like Python which use whitespace as a block delimeter.

blocks|key|1508234|text|不管你把星号放在哪里，所有的语句都会创建NSString类型的指针。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508235|但是，当在一行中使用多个变量名时，您必须为每个变量写上星号。|1508236|NSString+*+nsstring,+*+nsstring2;|code-block|syntax|javascript|1508237|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

it doesn't matter where you put your asterisk, all statements create pointers of type NSString.

when using multiple variable names in one line you have to write the asterisk for each variable though.

<pre><code>NSString * nsstring, * nsstring2;
</code></pre>

blocks|key|1293785|text|没有区别，*放在指针声明中的位置无关紧要。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1293786|entityMap^0|5|1|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|K|8|@]|D|@]|E|$]]]|G|$]]

There is no difference, where the <code>*</code> is placed in a pointer declaration is irrelevant.

blocks|key|1293861|text|没有区别，空白位置是无关紧要的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1293862|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

No difference, whitespace placement is irrelevant.

blocks|key|1508652|text|这是绝对没有区别的。NSString+*+myString和NSString+*+mystring是相同的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508653|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

There is absolutely no difference. NSString* mystring and NSString *myString are identical.

blocks|key|1508028|text|实际上所有这些都是等价的:指向nsstring的指针！！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508029|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

there actually all equivalent: a pointer to an nsstring!!

blocks|key|1508697|text|*的工作方式与标准C中的相同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508698|这是一个很好的入门读物，介绍了将*放在不同的位置以及它的用途：http://boredzo.org/pointers/|offset|length|1508699|entityMap|0|LINK|mutability|MUTABLE|url|http://boredzo.org/pointers/^0|0|V|S|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

the * works the same way as it does in standard C.

this is a nice primer on putting the * in different places and what it does:
<a href="http://boredzo.org/pointers/" rel="nofollow noreferrer">http://boredzo.org/pointers/</a>

blocks|key|1508483|text|这两者之间绝对没有区别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1508484|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

There is absolutely no difference between these.

blocks|key|1293645|text|1、2和4是等价的，它们定义了一个指向NSString的指针。我个人的偏好是尽可能多地模仿K&R，所以我喜欢使用NSString+*string;|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1293646|虽然(NString*)string;是一个有效的语句，但它本身并不能做任何事情。|1293647|$+cat+foo.m
#include+<Cocoa/Cocoa.h>

void+foo()
{
++++NSString+*string;

++++(NSString*)+string;++//+doesn't+do+anything
++++42;+++//+doesn't+do+anything+either
}

$+gcc+-Wall+-c+foo.m
foo.m:+In+function+'foo':
foo.m:7:+warning:+statement+with+no+effect
foo.m:8:+warning:+statement+with+no+effect|code-block|syntax|javascript|1293648|entityMap^0|1K|H|0|2|H|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|U|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|N|$]]

1, 2 and 4 are equivalent and define a pointer to an NSString. My personal preference is to emulate K&amp;R as much as possible, so I like to use <code>NSString *string;</code>

<code>(NString*)string;</code> though a valid statement, doesn't really do anything by itself.

<pre><code>$ cat foo.m
#include &lt;Cocoa/Cocoa.h&gt;

void foo()
{
 NSString *string;

 (NSString*) string; // doesn't do anything
 42; // doesn't do anything either
}

$ gcc -Wall -c foo.m
foo.m: In function 'foo':
foo.m:7: warning: statement with no effect
foo.m:8: warning: statement with no effect
</code></pre>

blocks|key|1294080|text|在xcode4文档示例代码中，您可以始终看到3.例如，在MoveMeView.m中|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1294081|#if+1

-+(void)growAnimationDidStop:(NSString+*)animationID+finished:(NSNumber+*)finished+context:(void+*)context+{

#define+MOVE_ANIMATION_DURATION_SECONDS+0.15

[UIView+beginAnimations:nil+context:NULL];
[UIView+setAnimationDuration:MOVE_ANIMATION_DURATION_SECONDS];
placardView.transform+=+CGAffineTransformMakeScale(1.1f,+1.1f);+
/*
+Move+the+placardView+to+under+the+touch.
+We+passed+the+location+wrapped+in+an+NSValue+as+the+context.
+Get+the+point+from+the+value,+then+release+the+value+because+we+retained+it+in+touchesBegan:withEvent:.
+*/
NSValue+*touchPointValue+=+(NSValue+*)context;
placardView.center+=+[touchPointValue+CGPointValue];
[touchPointValue+release];
[UIView+commitAnimations];
}|code-block|syntax|javascript|1294082|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

in the xcode4 documentation sample code you can see 3. all the time, for example in MoveMeView.m 

<pre><code>#if 1

- (void)growAnimationDidStop:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {

#define MOVE_ANIMATION_DURATION_SECONDS 0.15

[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:MOVE_ANIMATION_DURATION_SECONDS];
placardView.transform = CGAffineTransformMakeScale(1.1f, 1.1f); 
/*
 Move the placardView to under the touch.
 We passed the location wrapped in an NSValue as the context.
 Get the point from the value, then release the value because we retained it in touchesBegan:withEvent:.
 */
NSValue *touchPointValue = (NSValue *)context;
placardView.center = [touchPointValue CGPointValue];
[touchPointValue release];
[UIView commitAnimations];
}
</code></pre>

blocks|key|1294135|text|计算机的备选方案1、2和4可能没有任何区别，但代码的其他阅读器有区别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1294136|因为像https://stackoverflow.com/a/1521382、https://stackoverflow.com/a/16040884和https://www.tutorialspoint.com/objective_c/objective_c_pointers.htm这样的解释使用的是第一种选择：|offset|length|1294137|1.++NSString+*string;|style|CODE|1294138|所有额外的变量都需要有自己的星号，如下所示：|1294139|NSString+*aString,+*bString;|1294140|我的谦虚建议是，我们使用备选方案1作为标准。|1294141|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/1521382|1|https://stackoverflow.com/a/16040884|2|https://www.tutorialspoint.com/objective_c/objective_c_pointers.htm^0|0|3|Z|0|13|10|1|24|1V|2|0|0|L|0|0|0|S|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|12|8|@]|9|@$D|13|E|14|1|15]|$D|16|E|17|1|18]|$D|19|E|1A|1|1B]]|A|$]]|$1|F|3|G|5|6|7|1C|8|@$D|1D|E|1E|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|1F|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1G|8|@$D|1H|E|1I|H|I]]|9|@]|A|$]]|$1|N|3|O|5|6|7|1J|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|Q|$R|$5|S|T|U|A|$V|W]]|X|$5|S|T|U|A|$V|Y]]|Z|$5|S|T|U|A|$V|10]]]]

There may not be any differences in the alternatives 1, 2 and 4 to the computer but there are to other readers of the code.

Since explanations like <a href="https://stackoverflow.com/a/1521382">https://stackoverflow.com/a/1521382</a> and <a href="https://stackoverflow.com/a/16040884">https://stackoverflow.com/a/16040884</a> and <a href="https://www.tutorialspoint.com/objective_c/objective_c_pointers.htm" rel="nofollow noreferrer">https://www.tutorialspoint.com/objective_c/objective_c_pointers.htm</a> use the first alternative:

<code>1. NSString *string;</code>

and all extra variables need their own asterisk like in:

<code>NSString *aString, *bString;</code>

my humble suggestion is that we use alternative 1 as a standard.

I have just begun learning Objective-C, coming from a VB .Net and C# .Net background. I understand pointer usage, but in Objective-C examples I see the asterisk placed in several different places, and search as I might, I have not been able to find an answer as to why this is. Every search I try turns up all kinds of explanations about pointers (which I really don't need), but not a single mention of the reasons/effects of the different placements of the asterisk. Here are some examples I've seen:

<pre><code>NSString *string;
NSString * string;
(NSString *) string;
NSString* string;
</code></pre>

What do these different positions of the asterisk mean? I'm sure it's a simple answer but it's frustrating not being able to find it in any of the Apple tutorial and reference documentation or online so far.

Can someone please end my misery and answer this perplexing question? Thanks!

Placement of the asterisk in Objective-C

Objective-C

编译器

Python

我刚刚开始学习Objective-C，来自VB .Net和C# .Net背景。我理解指针的用法，但在Objective-C示例中，我看到星号放在几个不同的位置，尽管我可能会搜索，但我无法找到原因的答案。我尝试的每一次搜索都会找到关于指针的各种解释(我真的不需要)，但没有提到星号不同位置的原因/影响。下面是我见过的一些例子：NSString *string;NSString * string;(NS

问星号在Objective-C中的位置
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