blocks|key|1838497|text|前两个或本质上相同|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1838498|然而，后者不是，因为userName在那时是一个无效的字符串对象。|1838499|但是，将其更改为|1838500|userName+=+[[[NSString+alloc]+initWithString:@"Caroline"]+autorelease];|code-block|syntax|javascript|1838501|将使它实际上与前两个相同。|1838502|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|R|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The first two or essentially the same

The latter one is not however as userName would be an invalid string object at that point.

However changing it to 

<pre><code>userName = [[[NSString alloc] initWithString:@"Caroline"] autorelease];
</code></pre>

would render it effectively the same as the previous two.

blocks|key|1838520|text|版本01:是一个字符串常量...版本02:通过复制常量创建的自动释放的NSString。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1838521|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|$]]

version 01: is a string constant....
version 02: is an auto-released NSString created by copying a constant.

blocks|key|1951842|text|它们都是相似的，但三者之间有一些细微的区别。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1951843|第一个是指向字符串常量的指针。字符串Teddy存储在只读内存中，userName是指向此字符串常量的指针。您不需要(也不能)保留或释放此对象，因为它“永久”存在(即，在程序的持续时间内)。|offset|length|style|CODE|1951844|第二个是内容为Gary的自动释放字符串对象。当返回给您时，它的释放计数为0。它可以根据需要保留和发布。|1951845|第三个类似于第二个，但它不是自动释放的，所以在最初返回给您时，它的保留计数为1。像第二个一样，它可以根据需要保留和发布。|1951846|entityMap^0|0|I|5|W|8|0|7|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@$D|P|E|Q|F|G]|$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|T|8|@$D|U|E|V|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|W|8|@]|9|@]|A|$]]|$1|L|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|M|$]]

They are all similar, but there are some slight differences between the three.

The first one is a pointer to a string constant. The string <code>Teddy</code> is stored in read-only memory, and <code>userName</code> is a pointer to this string constant. You need not (and cannot) retain or release this object, since it exists "permanently" (that is, for the duration of the program).

The second one is an autoreleased string object with the contents <code>Gary</code>. When returned to you, it has a release count of 0. It may be retained and released as needed.

The third one is similar to the second one, but it is not autoreleased, so it has a retain count of 1 when it is initially returned to you. Like the second one, it may be retained and released as needed.

blocks|key|1951908|text|这些实例中的大部分差异在于内存的管理方式。如果您想更清楚地了解后台发生了什么，您可能需要仔细阅读Objective-C+Memory+Management+Guide。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1951909|//+Version_01
userName+=+@"Teddy";|code-block|syntax|javascript|1951910|这是一个字符串常量，它没有任何与之相关的内存管理。用于保存该值的内存是代码(本质上)所在的内存的一部分。对该变量的retain和release调用将被忽略。|style|CODE|1951911|//+Version_02
userName+=+[NSString+stringWithString:@"Gary"];|1951912|这是NSString对象的autoreleased实例。它的保留计数当前是1，除非它被保留，否则将很快被自动释放池释放。|1951913|//+Version_03
userName+=+[[NSString+alloc]+initWithString:@"Caroline"];
[userName+release];|1951914|这是NSString的托管实例。当它第一次初始化时，它的保留计数是1。在释放它之后，保留计数下降到零，因此，它的内存将被释放。在释放变量userName之后引用它会导致EXE_BAD_ACCESS错误。|1951915|entityMap|0|LINK|mutability|MUTABLE|url|http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html|1|http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/MemoryMgmt/Articles/mmAutoreleasePools.html#//apple_ref/doc/uid/20000047-CJBFBEDI^0|1C|Z|0|0|0|1L|6|1S|7|0|0|D|C|1|0|0|1W|8|2C|E|0^^$0|@$1|2|3|4|5|6|7|14|8|@]|9|@$A|15|B|16|1|17]]|C|$]]|$1|D|3|E|5|F|7|18|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|19|8|@$A|1A|B|1B|K|L]|$A|1C|B|1D|K|L]]|9|@]|C|$]]|$1|M|3|N|5|F|7|1E|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|1F|8|@]|9|@$A|1G|B|1H|1|1I]]|C|$]]|$1|Q|3|R|5|F|7|1J|8|@]|9|@]|C|$G|H]]|$1|S|3|T|5|6|7|1K|8|@$A|1L|B|1M|K|L]|$A|1N|B|1O|K|L]]|9|@]|C|$]]|$1|U|3|-4|5|6|7|1P|8|@]|9|@]|C|$]]]|V|$W|$5|X|Y|Z|C|$10|11]]|12|$5|X|Y|Z|C|$10|13]]]]

Most of the differences in these instances is how the memory is managed. If you want a clearer view of what's happening in the background, you might want to peruse the <a href="http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/MemoryMgmt/MemoryMgmt.html" rel="nofollow noreferrer">Objective-C Memory Management Guide</a>.

<pre><code>// Version_01
userName = @"Teddy";
</code></pre>

This is a String constant that does not have any memory management associated with it. The memory used to hold the value is part of the memory in which the code resides in (essentially). <code>retain</code> and <code>release</code> calls on the variable will be ignored.

<pre><code>// Version_02
userName = [NSString stringWithString:@"Gary"];
</code></pre>

This is an <a href="http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/MemoryMgmt/Articles/mmAutoreleasePools.html#//apple_ref/doc/uid/20000047-CJBFBEDI" rel="nofollow noreferrer">autoreleased</a> instance of an NSString object. Its retain count is currently one and will be released by the autorelease pool soon unless it is retained.

<pre><code>// Version_03
userName = [[NSString alloc] initWithString:@"Caroline"];
[userName release];
</code></pre>

This is a managed instance of an NSString. When it is first initialized, its retain count is one. After releasing it, the retain count went down to zero, therefore, its memory will be deallocated. Referring to the variable <code>userName</code> after releasing it will cause an <code>EXE_BAD_ACCESS</code> error.

blocks|key|538910|text|实际上，只要在释放Version_03字符串后不尝试使用它，就没有什么不同。如果你想这样做，你需要用_auto_release代替它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|538911|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|$]]

Practically, there are no differences, as long as you don't attempt to use the Version_03 string after you release it. If you want to do that, you'll need to autorelease it instead.

I understand that the v03 example creates an object that I own and must ultimately release. What I would like to know is are there any differences between the first two(v_01 &amp; v02), or are they essentially the same?

<pre><code>// Version_01
userName = @"Teddy";

// Version_02
userName = [NSString stringWithString:@"Gary"];

// Version_03
userName = [[NSString alloc] initWithString:@"Caroline"];
... some code
[userName release];
</code></pre>

gary

Differences between NSStrings?

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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我知道v03示例创建了一个我拥有并最终必须释放的对象。我想知道的是，前两者(v_01和v02)之间有什么不同，或者它们本质上是相同的吗？// Version_01userName = @"Teddy";// Version_02userName = [NSString stringWithString:@"Gary"]...

问NSStrings之间的区别？
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问NSStrings之间的区别？EN