blocks|key|3077414|text|正如gaige所说，如果你发布一段代码而不是解释，它会更加清晰。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3077415|无论如何，您可以将您的工厂移到类方法中，这样您就不会有这样的问题了。我的意思是这样的：|3077416|MyClass*+instance+=+[MyClass+instanceWithParameters:params];

@interface+MyClass
%2B+(MyClass*)+instanceWithParameters:(ParamType)params;
@end|code-block|syntax|javascript|3077417|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|$]]

<p>As gaige said, it will be much more clearer if you post a piece of code rather than explanations.</p>

<p>Anyway, you can move your factory to the class method, so you will have no such problem at all. I mean something like this:</p>

<pre><code>MyClass* instance = [MyClass instanceWithParameters:params];

@interface MyClass
+ (MyClass*) instanceWithParameters:(ParamType)params;
@end
</code></pre>


blocks|key|3077441|text|您可以这样实现init，它应该释放self以平衡alloc调用中的保留计数。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3077442|-+(id)initWithSomething:(id)something
{
++++[self+release];+//+don't+need+this+line+for+ARC
++++self+=+nil;
++++return+[[PrivateSubClass+alloc]+initWithSomething:something];
}|code-block|syntax|javascript|3077443|如果经常将init作为工厂方法来实现的话。例如NSArray，NSDictionary，NSString|3077444|entityMap^0|7|4|H|4|O|5|0|0|5|4|N|7|V|C|18|8|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|N|$]]

<p>you can implemented <code>init</code> like this, which should release <code>self</code> to balance the retain count from <code>alloc</code> call.</p>

<pre><code>- (id)initWithSomething:(id)something
{
    [self release]; // don't need this line for ARC
    self = nil;
    return [[PrivateSubClass alloc] initWithSomething:something];
}
</code></pre>

<p>and it if very often to implement <code>init</code> as a factory method. e.g. <code>NSArray</code>, <code>NSDictionary</code>, <code>NSString</code></p>


blocks|key|967500|text|在不知道导致分析器行为的代码是什么的情况下，很难判断，但作为一般规则，这里有几种定义init/工厂方法的编译器友好的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|967501|经典alloc/init|967502|-+(instancetype)initWithParameter:(id)parameter+{
++++if(self+=+[super+init])+{
+++++++_parameter+=+parameter;+
++++}
++++return+self;
}|code-block|syntax|javascript|967503|用法|967504|MyCustomClass+*+myInstance+=+[[MyCustomClass+alloc]+initWithParameter:foo];|967505|这将产生一个具有%2B1保留计数的实例。在ARC下，这将被自动正确地管理，因为它遵循NARC规则(New，Alloc，rule，Copy)。出于同样的原因，在预ARC环境中，客户端必须显式地发布它.|967506|自定义工厂法|967507|圆弧|967508|%2B+(instancetype)canIHazInstanceWithParameter:(id)parameter+{
++++return+[[self+alloc]+initWithParameter:parameter];+//+assuming+-initWithParameter:+defined
}|967509|预弧|967510|%2B+(instancetype)canIHazInstanceWithParameter:(id)parameter+{
++++return+[[[self+alloc]+initWithParameter:parameter]+autorelease];+//+assuming+-initWithParameter:+defined
}|967511|967512|MyCustomClass+*+myInstance+=+[MyCustomClass+canIHazInstanceWithParameter:foo];|967513|在ARC和预ARC中，该方法都返回一个自动释放的实例(在预ARC实现中这显然更明确)，它不需要由客户端管理。|967514|备注|967515|您可能注意到了instancetype关键字。这是Clang引入的一个方便的语言延伸，在实现您自己的构造函数/工厂方法时，它将编译器变成一个好朋友。我写了关于这个问题的文章，这可能和你有关。|unordered-list-item|offset|length|style|CODE|967516|工厂方法是否优于init方法是值得商榷的。从客户端的角度来看，它在ARC下没有多大区别，前提是您要小心遵循命名约定，即使我个人倾向于在接口中公开工厂方法，而只在内部实现自定义init方法(正如我在上面的示例中所做的那样)。与其说这是一个实际的问题，不如说是一个风格的问题。|967517|entityMap|0|LINK|mutability|MUTABLE|url|http://clang.llvm.org/docs/LanguageExtensions.html|1|http://www.codepills.net/blog/2013/01/01/obj-c-infer-types-like-a-man-man/^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|7|C|12|4|0|2C|2|1|0|8|4|2F|4|0^^$0|@$1|2|3|4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|1R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|1S|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|1T|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1U|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1V|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|1W|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|1X|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1Y|8|@]|9|@]|A|$G|H]]|$1|Y|3|J|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|Z|3|10|5|F|7|20|8|@]|9|@]|A|$G|H]]|$1|11|3|12|5|6|7|21|8|@]|9|@]|A|$]]|$1|13|3|14|5|6|7|22|8|@]|9|@]|A|$]]|$1|15|3|16|5|17|7|23|8|@$18|24|19|25|1A|1B]]|9|@$18|26|19|27|1|28]|$18|29|19|2A|1|2B]]|A|$]]|$1|1C|3|1D|5|17|7|2C|8|@$18|2D|19|2E|1A|1B]|$18|2F|19|2G|1A|1B]]|9|@]|A|$]]|$1|1E|3|-4|5|6|7|2H|8|@]|9|@]|A|$]]]|1F|$1G|$5|1H|1I|1J|A|$1K|1L]]|1M|$5|1H|1I|1J|A|$1K|1N]]]]

<p>Without knowing what is the code that is causing the analyzer's behavior it's hard to tell, but as a general rule, here's a couple of compiler-friendly ways to define init/factory methods.</p>

<h2>Classic alloc/init</h2>

<pre><code>- (instancetype)initWithParameter:(id)parameter {
    if(self = [super init]) {
       _parameter = parameter; 
    }
    return self;
}
</code></pre>

<h3>Usage</h3>

<pre><code>MyCustomClass * myInstance = [[MyCustomClass alloc] initWithParameter:foo];
</code></pre>

<p>This will produce an instance with a +1 retain count. Under ARC this will be automatically managed properly since it follows the NARC rule (New, Alloc, Retain, Copy).
For the same reason, in pre-ARC environments it has to be explicitly released by the client.</p>

<h2>Custom factory method</h2>

<h3>ARC</h3>

<pre><code>+ (instancetype)canIHazInstanceWithParameter:(id)parameter {
    return [[self alloc] initWithParameter:parameter]; // assuming -initWithParameter: defined
}
</code></pre>

<h3>Pre-ARC</h3>

<pre><code>+ (instancetype)canIHazInstanceWithParameter:(id)parameter {
    return [[[self alloc] initWithParameter:parameter] autorelease]; // assuming -initWithParameter: defined
}
</code></pre>

<h3>Usage</h3>

<pre><code>MyCustomClass * myInstance = [MyCustomClass canIHazInstanceWithParameter:foo];
</code></pre>

<p>Both in ARC and pre-ARC the method returns an autoreleased instance (this is clearly more explicit in the pre-ARC implementation), which doesn't have to be managed by the client.</p>

<h2>Remarks</h2>

<ul>
<li><p>You may have noticed the <code>instancetype</code> keyword. That's a handy <a href="http://clang.llvm.org/docs/LanguageExtensions.html" rel="nofollow">language extension</a> introduced by Clang, that turns the compiler into a dear friend when implementing your own constructors/factory methods. I wrote <a href="http://www.codepills.net/blog/2013/01/01/obj-c-infer-types-like-a-man-man/" rel="nofollow">an article</a> on the subject, which may be relevant to you.</p></li>
<li><p>Whether factory methods are preferable to <code>init</code> methods is debatable. From a client perspective it does not make much difference under ARC, provided that you carefully follow the naming conventions, even though I personally tend to expose factory methods in the interface, while implementing custom <code>init</code> methods only internally (as I did in the examples above). It's more a matter of style than an actual practical concern.</p></li>
</ul>


<p>I implemented the old init-as-a-factory pattern, but in one particular case (but not others!) I get a warning from the analyser regarding memory leaks. And indeed, looking at the <a href="https://developer.apple.com/library/mac/#documentation/cocoa/Conceptual/MemoryMgmt/Articles/mmRules.html" rel="nofollow">Cocoa Memory Management Policy</a> rules, it is <code>alloc</code>, not <code>init</code>, which can return +1-retain-count objects.</p>

<p>So it appears that:</p>

<ol>
<li>Releasing <code>self</code> and returning a new object from <code>init</code> is, strictly speaking, against the rules.</li>
<li>Many places on the internet promote this technique, and because of the tandem nature of alloc/init this does work.</li>
<li>The analyser sometimes complains about this, and sometimes doesn't.</li>
</ol>

<p>So... have we been doing this wrong all along?</p>


Objective C - is init a bad place to implement a factory?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我实现了旧的init作为工厂模式，但在一个特定的情况下(而不是其他！)我收到分析器关于内存泄漏的警告。事实上，看看规则，可以返回+1保留计数对象的是alloc，而不是init。因此，看来：严格地说，释放self并从init返回一个新对象是违反规则的。互联网上的许多地方都在推广这种技术，而且由于alloc/init的串联...

问目标C-这是不是一个实施工厂的坏地方？
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问目标C-这是不是一个实施工厂的坏地方？EN