blocks|key|2134955|text|当然，PHP的数组是一个有序映射。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2134956|但是Symfony的OrderedHashMap与PHP的数组有一些不同的行为(比如特性)。|offset|length|style|CODE|2134957|OrderedHashMap支持迭代期间的并发修改。这意味着您可以在foreach循环中插入和删除元素，迭代器将相应地反映这些更改。但是迭代中的array是复制的(在写上复制)，任何修改都不会反映在循环中。|2134958|$map+=+new+OrderedHashMap();
$map[1]+=+1;
$map[2]+=+2;
$map[3]+=+3;

foreach+($map+as+$index+=>+$value)+{
++++echo+"$index:+$value\n"
++++if+(1+===+$index)+{
++++++++$map[1]+=+4;
++++++++$map[]+=+5;
++++}
}|code-block|syntax|javascript|2134959|如果使用array，您将得到不同的输出。在array的迭代中，循环将看不到数字5。|2134960|关于“为什么？”：在塞福尼(氏)码基中搜索。只有一个位置可以使用OrderedHashMap，它用于存储窗体的子级。new+InheritDataAwareIterator($this->children)使用它来迭代。所以我认为答案是帮助处理表单的孩子。|BOLD|2134961|多亏了@鱼骨：|2134962|因此，好处不是排序，而是在循环中修改它的能力。|blockquote|2134963|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/search?q=org%253Asymfony%2BOrderedHashMap&type=Code^0|0|A|E|0|0|E|Y|7|20|5|0|0|4|5|L|5|13|1|0|O|2|W|E|1M|19|A|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@$D|18|E|19|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|1A|8|@$D|1B|E|1C|F|G]|$D|1D|E|1E|F|G]|$D|1F|E|1G|F|G]]|9|@]|A|$]]|$1|J|3|K|5|L|7|1H|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|1I|8|@$D|1J|E|1K|F|G]|$D|1L|E|1M|F|G]|$D|1N|E|1O|F|G]]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1P|8|@$D|1Q|E|1R|F|S]|$D|1S|E|1T|F|G]|$D|1U|E|1V|F|G]]|9|@$D|1W|E|1X|1|1Y]]|A|$]]|$1|T|3|U|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|V|3|W|5|X|7|20|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|21|8|@]|9|@]|A|$]]]|Z|$10|$5|11|12|13|A|$14|15]]]]

Of course PHP's array is an ordered-map.

But Symfony's <code>OrderedHashMap</code> has some different behaviors (say, features) from PHP's array.

<code>OrderedHashMap</code> supports concurrent modification during iteration. That means that you can insert and remove elements from within a <code>foreach</code> loop and the iterator will reflect those changes accordingly. But <code>array</code> in the iteration is a copied one (Copy-On-Write), any modification is not reflected in the loop.

<pre><code>$map = new OrderedHashMap();
$map[1] = 1;
$map[2] = 2;
$map[3] = 3;

foreach ($map as $index =&gt; $value) {
 echo "$index: $value\n"
 if (1 === $index) {
 $map[1] = 4;
 $map[] = 5;
 }
}
</code></pre>

You will get different output if you are using <code>array</code>. In the iteration of an <code>array</code> the loop won't see the number <code>5</code>.

About "Why?": Search it in <a href="https://github.com/search?q=org%3Asymfony+OrderedHashMap&amp;type=Code" rel="nofollow noreferrer">Symfony's codebase</a>. There is only one place to use the <code>OrderedHashMap</code>, which is used to store a form's children. It's used by <code>new InheritDataAwareIterator($this-&gt;children)</code> to iterate. So I think the answer is to help to process the form's children.

And thanks to @fishbone:

<blockquote>
 So the benefit is not the ordering but the ability to modify it in loops.
</blockquote>

blocks|key|869070|text|通常，不仅在Symfony的上下文中，除了其他实现的特性之外，面向对象的结构比原始类型(如int、string或array+)更可取，因为它们可以被注入类中进行单元测试。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|869071|面向对象的结构也可以执行不变量，而原始类型只能保存数据而不存在任何行为。|869072|entityMap^0|19|3|1D|6|1K|5|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

In general, not only in Symfony's context, beside additional implemented features, object oriented structures are preferred over primitive types such as <code>int</code>, <code>string</code> or <code>array</code> as they can be injected into the class for unit testing.

Object oriented structures can enforce invariants as well whereas primitive types can only hold data without any behaviors.

Symfony provides an <code>OrderedHashMap</code>. Its <a href="https://api.symfony.com/3.4/Symfony/Component/Form/Util/OrderedHashMap.html" rel="nofollow noreferrer">documentation states</a>

<blockquote>
 Unlike associative arrays, the map keeps track of the order in which keys were added and removed. This order is reflected during iteration.
</blockquote>

I'm confused by this statement, because I thought PHP associative arrays are actually already ordered maps. I found this question on SO, which confirms my previous assumption: <a href="https://stackoverflow.com/q/10914730/395879">Are PHP Associative Arrays ordered?</a>

I wonder, if the Symfony devs didn't know PHP arrays are already ordered maps or if I don't understand the role of Symfony's <code>OrderedHashMap</code>

Why does Symfony provide an OrderedHashMap

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。

文章

问答

视频

学习中心

腾讯云实验室

直播

竞赛

腾讯云代码分析专区

腾讯iOA零信任安全管理系统专区

腾讯云架构师技术同盟交流圈

腾讯云数据库专区

腾讯云顾问专区

腾讯云原生专区

腾讯混元专区

腾讯云TCE专区

腾讯云Lighthouse专区

腾讯云HAI专区

腾讯云Edgeone专区

腾讯云存储专区

腾讯云智能专区

腾讯轻联专区 

腾讯云开发专区

TAPD专区

腾讯轻量云游戏服专区

腾讯云最具价值专家

腾讯云架构师技术同盟

腾讯云创作之星

腾讯云开发者先锋

腾讯云代码助手

云原生构建

TAPD 敏捷项目管理

Cloud Studio

SDK中心

API中心

命令行工具

涵盖代码开发、场景应用、自动测试全流程，助你从零构建专属AI助手

一站式MCP教程库，解锁AI应用新玩法

Symfony提供了一个OrderedHashMap。Its 与关联数组不同，映射跟踪添加和删除键的顺序。这个顺序反映在迭代过程中。我对这句话感到困惑，因为我认为PHP关联数组实际上已经是有序映射了。我在SO上找到了这个问题，这证实了我先前的假设：我想知道，如果Symfony开发者不知道PHP数组已经是有序映射，还是我...

问为什么Symfony提供一个OrderedHashMap
EN

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问为什么Symfony提供一个OrderedHashMapEN

社区

活动

圈层

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问为什么Symfony提供一个OrderedHashMap
EN