blocks|key|3169255|text|错误消息会告诉您答案。您应该将classBReference定义为property，或者将classBReference定义为ivar。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3169256|entityMap^0|F|F|19|F|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

The error message tells you the answer. You should define <code>classBReference</code> as property or use <code>classBReference</code> as ivar.

blocks|key|5291431|text|通过避免使用全局变量(也就是单例变量)，听起来就不会那么困惑了。当C创建B时，为B提供对C的引用。当D创建B时，为C提供对D的引用。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|5291432|如果需要避免保留周期，请对B进行反向引用：weak+(如果您的部署目标至少是iOS+5.0)或unsafe_unretained+(如果您的部署目标早于iOS+5.0)。|5291433|entityMap^0|X|1|10|1|14|1|18|1|1E|1|1H|1|1L|1|1P|1|0|D|1|L|4|1B|H|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|I|$]]

It sounds like you'd be less confused by avoiding the global variable (aka singleton). Give the <code>C</code> a reference to the <code>B</code> when the <code>B</code> creates the <code>C</code>. Give the <code>D</code> a reference to the <code>B</code> when the <code>C</code> creates the <code>D</code>.

If you need to avoid a retain cycle, make the back-references to the <code>B</code> either <code>weak</code> (if your deployment target is at least iOS 5.0) or <code>unsafe_unretained</code> (if your deployment target is earlier than iOS 5.0).

blocks|key|3169456|text|点和箭头|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3169457|“点符号”是Objective-C中最近添加的一个符号，它为访问器提供了一种简写符号。如果有指向对象(或结构！)的指针，则不能使用.访问其实例变量，只能使用->访问。|offset|length|style|CODE|3169458|你的产品线|3169459|sharedInstance.classBReference+=+self;|code-block|syntax|javascript|3169460|完全相同于|3169461|[sharedInstance+setClassBReference:self];|3169462|问题是您没有任何这样的方法-setClassBReference:。为了设置实例变量，您必须改为编写|3169463|sharedInstance->classBReference+=+self;|3169464|@受保护的变量|3169465|在使用下面这行代码切换行之后，您可能会看到错误(如果您还没有使用@public)|3169466|3169467|实例变量“classBReference”是私有的|blockquote|3169468|3169469|3169470|在这种情况下，您需要更改classA接口，以便将classBReference声明为@public。classA中的实例变量列表应该如下所示|3169471|@interface+classA+:+NSObject
{
//@protected
//(The+@protected+keyword+is+optional+when+at+the+beginning+of+the+list;+instance
//variables+are+protected+by+default,+which+is+why+you're+needing+to+declare+your
//instance+variable+classBReference+to+be+@public+(since+classB+is+not+a+subclass
//of+classA+and+consequently+cannot+access+its+protected+instance+variables).
++++//....
++++//some+protected+instance+variables
++++//....
@private
++++//....
++++//some+private+instance+variables
++++//....
@public
++++//....
++++//some+public+instance+variables
++++classB+*classBReference;
++++//....
@protected
++++//....
++++//some+more+protected+instance+variables
++++//Note+that+@protected+is+not+optional+in+order+to+make+the+instance+variables
++++//here+be+protected+since+they+are+declared+subsequent+to+the+prior+@public.
++++//....
}
//....
@end|3169472|使用@properties|3169473|classBReference的案例|3169474|尽管如此，人们普遍认为使用访问器而不是实例变量是更好的做法。为此，您应该向classA接口添加一个属性：|3169475|@interface+classA+:+NSObject
{
++++classB+*classBReference;
}
@property+classB+*classBReference;
@end|3169476|并合成classBReference+属性以在classA的实现中访问classBReference+实例变量，如下所示：|BOLD|3169477|@implementation+classB

@synthesize+classBReference+=+classBReference;|3169478|一般设置|3169479|因为我们有一个实例变量和一个同名的属性，所以@synthesize不太清楚。一些澄清是必要的。通常，在类的(本例中为“MyObject”)中，@interface声明了一个实例变量(本例中为“myVariable”)和一个属性(本例中为“myProperty”)。|3169480|@interface+MyObject+:+NSObject
{
++++SomeObject+*myVariable;
}
@property+SomeObject+*myProperty;
@end|3169481|在类的@implementation中，有一行|3169482|@synthesize+myProperty+=+myVariable.|3169483|此代码的结果是，给定一个实例|3169484|MyObject+*object+=+//...|3169485|在这个班级中，一个人能够写|3169486|SomeObject+*someObject+=+//...
[object+setMyProperty:someObject];|3169487|和|3169488|SomeObject+*someOtherObject+=+[object+myProperty];|3169489|在MyObject实例上调用-setMyProperty:的结果是，myVariable被设置为等于传递给该方法的参数--在本例中为someObject。类似地，在MyObject实例上调用-myProperty的结果是返回myVariable。|3169490|它能给我们带来什么？|3169491|如果没有@property和@synthesize指令，就必须声明这些方法|3169492|-+(void)setMyProperty:(SomeObject+*)myProperty;
-+(SomeObject+*)myProperty;|3169493|手动定义，也可以手动定义：|3169494|-+(void)setMyProperty:(SomeObject+*)myProperty
{
++++myVariable+=+myProperty;
}

-+(SomeObject+*)myProperty
{
++++return+myVariable;
}|3169495|@property和@synthesize对此代码进行了一些删节。当您使用各种property+attributes时，为您生成的代码量将变得更加有益。|3169496|注意：有关于@property和@synthesize指令的more+to+say。首先，您不仅可以省略变量名来编写@synthesize+myProperty;，还可以完全省略myProperty的合成，并且在这两种情况下自动使用的变量名是不同的。|3169497|关于点符号的更多信息|3169498|问题中的点符号提供了另一层缩写。而不是必须编写|3169499|[object+setMyProperty:someObject];|3169500|现在，您可以编写|3169501|object.myProperty+=+someObject;|3169502|类似地，不需要编写|3169503|SomeObject+*someOtherObject+=+[object+myProperty];|3169504|3169505|SomeObject+*someOtherObject+=+object.myProperty;|3169506|重要的是要注意，这只是，只是符号。虽然当我们“将object.myProperty设置为someObject”时，它“看起来有点像”我们在做简单的赋值，但事实并非如此。特别是，当我们执行这行代码时|3169507|object.myProperty+=+someObject;|3169508|该方法|3169509|-+(void)setMyProperty:(SomeObject+*)someObject|3169510|将被执行。出于这个原因，dot+notation+is+a+subject+of+some+contention。这很方便，但重要的是要记住您的代码正在做什么。|3169511|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html#//apple_ref/doc/uid/TP30001163-CH17-SW2|1|https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html|2|http://weblog.bignerdranch.com/83-83/|3|http://qualitycoding.org/dot-notation/|4|https://stackoverflow.com/questions/6292753/dot-notation-vs-square-brackets-and-casting-in-objective-c|5|http://fernmac.blogspot.com/2012/04/objective-c-dot-notation-or-message.html|6|http://eschatologist.net/blog/?p=160|7|http://www.bit-101.com/blog/?p=2227|8|http://iphonedevelopment.blogspot.com/2009/08/dot-notation-controversy.html|9|http://jrfom.com/2010/06/16/objective-c-dot-notation/^0|0|1T|1|26|2|0|0|0|0|0|D|K|0|0|0|W|7|0|0|5|F|0|0|0|C|6|O|F|16|7|1E|6|0|0|0|0|11|6|0|0|3|F|N|6|Z|F|J|2|1F|4|0|0|0|M|B|1N|8|1Z|A|2O|A|3B|A|0|0|3|F|0|0|0|0|0|0|0|0|1|8|E|F|Y|A|1U|A|2A|8|2N|B|34|A|0|0|4|9|E|B|0|0|0|0|0|9|A|B|13|J|0|0|0|2|6|9|G|B|1M|N|2H|A|U|B|1|0|0|0|0|0|0|0|0|0|0|B|5|O|H|18|A|0|0|0|0|C|3|2|G|8|3|P|2|4|S|1|5|U|7|6|12|2|7|15|4|8|1A|A|9|0^^$0|@$1|2|3|4|5|6|7|46|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|47|8|@$D|48|E|49|F|G]|$D|4A|E|4B|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|4C|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|4D|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|4E|8|@]|9|@]|A|$]]|$1|Q|3|R|5|L|7|4F|8|@]|9|@]|A|$M|N]]|$1|S|3|T|5|6|7|4G|8|@$D|4H|E|4I|F|G]]|9|@]|A|$]]|$1|U|3|V|5|L|7|4J|8|@]|9|@]|A|$M|N]]|$1|W|3|X|5|6|7|4K|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|6|7|4L|8|@$D|4M|E|4N|F|G]]|9|@]|A|$]]|$1|10|3|-4|5|6|7|4O|8|@]|9|@]|A|$]]|$1|11|3|12|5|13|7|4P|8|@$D|4Q|E|4R|F|G]]|9|@]|A|$]]|$1|14|3|-4|5|6|7|4S|8|@]|9|@]|A|$]]|$1|15|3|-4|5|6|7|4T|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|4U|8|@$D|4V|E|4W|F|G]|$D|4X|E|4Y|F|G]|$D|4Z|E|50|F|G]|$D|51|E|52|F|G]]|9|@]|A|$]]|$1|18|3|19|5|L|7|53|8|@]|9|@]|A|$M|N]]|$1|1A|3|1B|5|6|7|54|8|@]|9|@]|A|$]]|$1|1C|3|1D|5|6|7|55|8|@]|9|@]|A|$]]|$1|1E|3|1F|5|6|7|56|8|@$D|57|E|58|F|G]]|9|@]|A|$]]|$1|1G|3|1H|5|L|7|59|8|@]|9|@]|A|$M|N]]|$1|1I|3|1J|5|6|7|5A|8|@$D|5B|E|5C|F|G]|$D|5D|E|5E|F|G]|$D|5F|E|5G|F|G]|$D|5H|E|5I|F|1K]|$D|5J|E|5K|F|1K]]|9|@]|A|$]]|$1|1L|3|1M|5|L|7|5L|8|@]|9|@]|A|$M|N]]|$1|1N|3|1O|5|6|7|5M|8|@]|9|@]|A|$]]|$1|1P|3|1Q|5|6|7|5N|8|@$D|5O|E|5P|F|G]|$D|5Q|E|5R|F|G]|$D|5S|E|5T|F|G]|$D|5U|E|5V|F|G]|$D|5W|E|5X|F|G]]|9|@]|A|$]]|$1|1R|3|1S|5|L|7|5Y|8|@]|9|@]|A|$M|N]]|$1|1T|3|1U|5|6|7|5Z|8|@$D|60|E|61|F|G]]|9|@]|A|$]]|$1|1V|3|1W|5|L|7|62|8|@]|9|@]|A|$M|N]]|$1|1X|3|1Y|5|6|7|63|8|@]|9|@]|A|$]]|$1|1Z|3|20|5|L|7|64|8|@]|9|@]|A|$M|N]]|$1|21|3|22|5|6|7|65|8|@]|9|@]|A|$]]|$1|23|3|24|5|L|7|66|8|@]|9|@]|A|$M|N]]|$1|25|3|26|5|6|7|67|8|@]|9|@]|A|$]]|$1|27|3|28|5|L|7|68|8|@]|9|@]|A|$M|N]]|$1|29|3|2A|5|6|7|69|8|@$D|6A|E|6B|F|G]|$D|6C|E|6D|F|G]|$D|6E|E|6F|F|G]|$D|6G|E|6H|F|G]|$D|6I|E|6J|F|G]|$D|6K|E|6L|F|G]|$D|6M|E|6N|F|G]]|9|@]|A|$]]|$1|2B|3|2C|5|6|7|6O|8|@]|9|@]|A|$]]|$1|2D|3|2E|5|6|7|6P|8|@$D|6Q|E|6R|F|G]|$D|6S|E|6T|F|G]]|9|@]|A|$]]|$1|2F|3|2G|5|L|7|6U|8|@]|9|@]|A|$M|N]]|$1|2H|3|2I|5|6|7|6V|8|@]|9|@]|A|$]]|$1|2J|3|2K|5|L|7|6W|8|@]|9|@]|A|$M|N]]|$1|2L|3|2M|5|6|7|6X|8|@$D|6Y|E|6Z|F|G]|$D|70|E|71|F|G]]|9|@$D|72|E|73|1|74]]|A|$]]|$1|2N|3|2O|5|6|7|75|8|@$D|76|E|77|F|1K]|$D|78|E|79|F|G]|$D|7A|E|7B|F|G]|$D|7C|E|7D|F|G]|$D|7E|E|7F|F|G]]|9|@$D|7G|E|7H|1|7I]]|A|$]]|$1|2P|3|2Q|5|6|7|7J|8|@]|9|@]|A|$]]|$1|2R|3|2S|5|6|7|7K|8|@]|9|@]|A|$]]|$1|2T|3|2U|5|L|7|7L|8|@]|9|@]|A|$M|N]]|$1|2V|3|2W|5|6|7|7M|8|@]|9|@]|A|$]]|$1|2X|3|2Y|5|L|7|7N|8|@]|9|@]|A|$M|N]]|$1|2Z|3|30|5|6|7|7O|8|@]|9|@]|A|$]]|$1|31|3|32|5|L|7|7P|8|@]|9|@]|A|$M|N]]|$1|33|3|2W|5|6|7|7Q|8|@]|9|@]|A|$]]|$1|34|3|35|5|L|7|7R|8|@]|9|@]|A|$M|N]]|$1|36|3|37|5|6|7|7S|8|@$D|7T|E|7U|F|1K]|$D|7V|E|7W|F|G]|$D|7X|E|7Y|F|G]]|9|@]|A|$]]|$1|38|3|39|5|L|7|7Z|8|@]|9|@]|A|$M|N]]|$1|3A|3|3B|5|6|7|80|8|@]|9|@]|A|$]]|$1|3C|3|3D|5|L|7|81|8|@]|9|@]|A|$M|N]]|$1|3E|3|3F|5|6|7|82|8|@]|9|@$D|83|E|84|1|85]|$D|86|E|87|1|88]|$D|89|E|8A|1|8B]|$D|8C|E|8D|1|8E]|$D|8F|E|8G|1|8H]|$D|8I|E|8J|1|8K]|$D|8L|E|8M|1|8N]|$D|8O|E|8P|1|8Q]]|A|$]]|$1|3G|3|-4|5|6|7|8R|8|@]|9|@]|A|$]]]|3H|$3I|$5|3J|3K|3L|A|$3M|3N]]|3O|$5|3J|3K|3L|A|$3M|3P]]|3Q|$5|3J|3K|3L|A|$3M|3R]]|3S|$5|3J|3K|3L|A|$3M|3T]]|3U|$5|3J|3K|3L|A|$3M|3V]]|3W|$5|3J|3K|3L|A|$3M|3X]]|3Y|$5|3J|3K|3L|A|$3M|3Z]]|40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<h1>Dots and Arrows</h1>

The "dot notation" is a somewhat recent addition to Objective-C and provides a shorthand notation for accessors. If you have a pointer to an object (or a struct!), you cannot access its instance variables with <code>.</code> but only with <code>-&gt;</code>. 

Your line

<pre><code>sharedInstance.classBReference = self;
</code></pre>

is exactly the same as

<pre><code>[sharedInstance setClassBReference:self];
</code></pre>

The problem is that you don't have any such method <code>-setClassBReference:</code>. In order to set the instance variable, you must instead write

<pre><code>sharedInstance-&gt;classBReference = self;
</code></pre>

<h2>@protected variables</h2>

After switching your line with this one, you may (if you haven't made it <code>@public</code>) see the error 

<blockquote>
 Instance variable '<code>classBReference</code>' is private
</blockquote>

In this case, you need to alter your <code>classA</code> interface so that <code>classBReference</code> is declared to be <code>@public</code>. Your list of instance variables in <code>classA</code> should look something like

<pre><code>@interface classA : NSObject
{
//@protected
//(The @protected keyword is optional when at the beginning of the list; instance
//variables are protected by default, which is why you're needing to declare your
//instance variable classBReference to be @public (since classB is not a subclass
//of classA and consequently cannot access its protected instance variables).
 //....
 //some protected instance variables
 //....
@private
 //....
 //some private instance variables
 //....
@public
 //....
 //some public instance variables
 classB *classBReference;
 //....
@protected
 //....
 //some more protected instance variables
 //Note that @protected is not optional in order to make the instance variables
 //here be protected since they are declared subsequent to the prior @public.
 //....
}
//....
@end
</code></pre>

<h2>Using @properties</h2>

<h3>The case of classBReference</h3>

That being said, it is widely regarded as a better practice to use accessors rather than instance variables in general. In order to do this, you should add a property to your <code>classA</code> interface:

<pre><code>@interface classA : NSObject
{
 classB *classBReference;
}
@property classB *classBReference;
@end
</code></pre>

and synthesize the <code>classBReference</code> property to access the <code>classBReference</code> instance variable in <code>classA</code>'s implementation as follows:

<pre><code>@implementation classB

@synthesize classBReference = classBReference;
</code></pre>

<h3>The general set-up</h3>

The <code>@synthesize</code> is somewhat unclear on account of the fact that we have both an instance variable and a property with the same name. Some clarification is in order. In general, in a class's ("<code>MyObject</code>" in this example) <code>@interface</code> one declares an instance variable ("<code>myVariable</code>" in this example) and a property ("<code>myProperty</code>" in this example).

<pre><code>@interface MyObject : NSObject
{
 SomeObject *myVariable;
}
@property SomeObject *myProperty;
@end
</code></pre>

In the class's <code>@implementation</code> one has the line

<pre><code>@synthesize myProperty = myVariable.
</code></pre>

The result of this code is that, given an instance 

<pre><code>MyObject *object = //...
</code></pre>

of the class, one is able to write

<pre><code>SomeObject *someObject = //...
[object setMyProperty:someObject];
</code></pre>

and 

<pre><code>SomeObject *someOtherObject = [object myProperty];
</code></pre>

The result of calling <code>-setMyProperty:</code> on the instance of <code>MyObject</code> is that <code>myVariable</code> is set equal to the argument passed into the method--in this case <code>someObject</code>. Similarly, the result of calling <code>-myProperty</code> on the instance of <code>MyObject</code> is that <code>myVariable</code> is returned.

<h3>What does it get us?</h3>

Without the <code>@property</code> and <code>@synthesize</code> directives, one would have to declare the methods

<pre><code>- (void)setMyProperty:(SomeObject *)myProperty;
- (SomeObject *)myProperty;
</code></pre>

manually and define them manually as well:

<pre><code>- (void)setMyProperty:(SomeObject *)myProperty
{
 myVariable = myProperty;
}

- (SomeObject *)myProperty
{
 return myVariable;
}
</code></pre>

The <code>@property</code> and <code>@synthesize</code> provide some abridgment to this code. The amount of code that is generated for you becomes even more beneficial when you use various of the <a href="https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html#//apple_ref/doc/uid/TP30001163-CH17-SW2" rel="nofollow noreferrer">property attributes</a>.

Note: There is <a href="https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html" rel="nofollow noreferrer">more to say</a> about the <code>@property</code> and <code>@synthesize</code> directives. For a start, not only can you write <code>@synthesize myProperty;</code> omitting the variable name, you can omit the synthesizing of <code>myProperty</code> entirely, and the variable names that are used automatically are different from one another in these two cases. 

<h2>A Bit More on Dot Notation</h2>

The dot notation from your question provides another layer of abbreviation. Rather than having to write

<pre><code>[object setMyProperty:someObject];
</code></pre>

you are now able to write

<pre><code>object.myProperty = someObject;
</code></pre>

Similarly, rather than having to write

<pre><code>SomeObject *someOtherObject = [object myProperty];
</code></pre>

you are now able to write

<pre><code>SomeObject *someOtherObject = object.myProperty;
</code></pre>

It is important to note that this is just just notation. Though it "kinda looks like" we're doing simple assignment when we "set <code>object.myProperty</code> equal to <code>someObject</code>", that is not the case. In particular, when we execute the line

<pre><code>object.myProperty = someObject;
</code></pre>

the method 

<pre><code>- (void)setMyProperty:(SomeObject *)someObject
</code></pre>

is executed. For this reason, <a href="http://weblog.bignerdranch.com/83-83/" rel="nofollow noreferrer">dot</a> <a href="http://qualitycoding.org/dot-notation/" rel="nofollow noreferrer">notation</a> <a href="https://stackoverflow.com/questions/6292753/dot-notation-vs-square-brackets-and-casting-in-objective-c">is</a> <a href="http://fernmac.blogspot.com/2012/04/objective-c-dot-notation-or-message.html" rel="nofollow noreferrer">a</a> <a href="http://eschatologist.net/blog/?p=160" rel="nofollow noreferrer">subject</a> <a href="http://www.bit-101.com/blog/?p=2227" rel="nofollow noreferrer">of</a> <a href="http://iphonedevelopment.blogspot.com/2009/08/dot-notation-controversy.html" rel="nofollow noreferrer">some</a> <a href="http://jrfom.com/2010/06/16/objective-c-dot-notation/" rel="nofollow noreferrer">contention</a>. It is a convenience, but it is important to keep in mind what your code is doing.

Let's say I have 2 classes, A and B. A is a singleton. I declare A in B, so I can access the singletons vars in methods in B.

B then creates an instance of another class, say class C.

C Then creates an instance of another class, say class D.

What I need to do is run a method in the instance of class B, from class D, and that's what is driving me nuts.

My first thought was to put a reference to the instance of class b, in my singleton (class A), something like...

<pre><code>sharedInstance.classBReference = self;
</code></pre>

..and then declare the singleton in Class D, and then use something like this in class D instance...

<pre><code>[sharedInstance.classBInstance classBInstanceMethod];
</code></pre>

But of course as soon as I did..

<pre><code>classB *classBReference;
</code></pre>

In the header of my singleton, it game me the "unknown type" which I read about on here, so instead, I put a 

<pre><code>@class classB;
</code></pre>

above the @interface, and then I was able to declare...

<pre><code>classB *classBReference;
</code></pre>

Without an error of unknown type, but in the init method of class B, this...

<pre><code>sharedInstance.classBReference = self;
</code></pre>

Still gives me an error of type

"property classBReference not found on objet of type "class A*" (the singleton) did you mean to access ivar classBReference?"

And I have no idea why it's doing that, what's the solution? or is there a better way to do what I'm trying to do?

storing instance reference in singleton in obj-c

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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假设我有两个类，A和B。A是一个单例。我在B中声明了A，这样我就可以在B中的方法中访问单例变量。然后，B创建另一个类的实例，比如类C。然后，C创建另一个类的实例，比如类D。我需要做的是在类B的实例中运行一个方法，来自类D，这就是让我发疯的原因。我的第一个想法是在我的单例(类A)中引用类b的实例，类似于...shared...

问在obj-c中的单例中存储实例引用
EN

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