blocks|key|1408468|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|entityMap^0^^$0|@$1|2|3|-4|4|5|6|B|7|@]|8|@]|9|$]]]|A|$]]

Sorry for the C# syntax, I'm not a PHP dev. But the core of the answer is language-agnostic, and I hope the syntax is readable enough for you to understand the focus of the examples.
<hr />
You've actually done a great job of listing ways to have one class use another, ordered ascendingly by looseness of the coupling.
<ul>
<li>Hardcoding a reference (tightest coupling)</li>
<li>Passing a method parameter with the object reference</li>
<li>Passing a contructor parameter with the object reference (loosest coupling)</li>
</ul>
<blockquote>
A friend of mine, who works for a lot of time with this, told me that is an error to use it in different ways, and that he always uses the constructor method, even if there is such a simple thing as a string helper.
</blockquote>
Your friend is mostly, but not completely on the right track.
For good practice, you always want to promote loose coupling. Loose coupling means that it's easier to swap out individual components when you need to. You might need to do so because you're making a change to your codebase, and having things loosely coupled mean that you can more easily target a specific component and swap it out without affecting the other components.
Another great example of loose coupling is the ability to unit test your code. In this answer, I'm going to use unit testing as the main use case here to highlight how coupling affects the ease of development. Just remember that the benefits of loose coupling are much bigger than just testability.
<hr />
Let's say we've developed the following class, and it currently hardcodes a dependency on <code>EmailSender</code>:
<pre><code>public class MyService
{
 public int Add(int a, int b)
 {
 var result = a + b;

 var emailSender = new EmailSender();
 emailSender.SendEmail(
 &quot;boss@company.com&quot;, 
 $&quot;Hey boss, I just calculated {a}+{b}, did you know that that is equal to {result}?&quot;
 );

 return result;
 }
}
</code></pre>
It's a silly example, but it serves the purpose I need it to. We want to test this service. However, we don't want to bombard our actual boss with emails about all our test runs.
While this is not relevant yet, I want you to look back at the code and think about what the consumer of this service needs to know to work with this service. All it needs to know is which numbers it needs to add, i.e. <code>a</code> and <code>b</code>. The consumer doesn't know about the mailsender specifically or how to operate it.
<hr />
By injecting the dependency, we make it possible to swap this mailsender out for a different one. When we run our test, we inject a fake mailsender which does not send an actual email, but does correctly confirm to us that someone tried to send an email.
Let's inject it as a method parameter, like you suggested.
<pre><code>public class MyService
{
 public int Add(int a, int b, IEmailSender emailSender)
 {
 var result = a + b;

 emailSender.SendEmail(
 &quot;boss@company.com&quot;, 
 $&quot;Hey boss, I just calculated {a}+{b}, did you know that that is equal to {result}?&quot;
 );

 return result;
 }
}

public interface IEmailSender
{
 void SendEmail(string to, string message);
}
</code></pre>
You can imagine the existence of a <code>EmailSender</code> class which actually sends out real emails.
Let's look at what a fake mailsender would look like:
<pre><code>public class FakeMailSender : IEmailSender 
{
 public void SendEmail(string to, string message)
 {
 // Snitch about what someone tried to do
 Console.WriteLine($&quot;Someone just tried to send an email to {to}&quot;);

 // DON'T SEND AN ACTUAL EMAIL
 }
}
</code></pre>
If I now want to test if <code>MyService</code> is working correctly, I can run a test where I inject a <code>FakeMailSender</code> instead of a real <code>EmailSender</code>. This doesn't affect the internal logic of <code>MyService</code> itself, which is what I'm testing. If <code>MyService</code> behaves correctly for a <code>FakeMailSender</code>, then I can rest assured that it will also behave correctly when I give it a real <code>EmailSender</code> (when deploying the code for real).
<hr />
However... Remember when I pointed out that the consumer of <code>MyService</code> only needed to know the numbers they needed to add?
That is sadly no longer the case. Now, they need to have access to some <code>IEmailSender</code> object and pass that along before they can add two numbers together? That means putting more work into their hands. The consumer is not going to like that, and they might possibly not even be allowed to know that we are secretly sending emails.
This is why we inject dependencies via the constructor. The constructor is separate from the public methods, and therefore we are able to separate the construction of the object from actually using the constructed object, which is really useful when the construction requires specific information (e.g. what kind of mailsender to use) even though you want to keep the usage short and simple (e.g. only knowing which numbers you want to add up).
<pre><code>public class MyService
{
 private IEmailSender _emailSender;

 public MyService(IEmailSender emailSender)
 {
 _emailSender = emailSender;
 }

 public int Add(int a, int b)
 {
 var result = a + b;

 _emailSender.SendEmail(
 &quot;boss@company.com&quot;, 
 $&quot;Hey boss, I just calculated {a}+{b}, did you know that that is equal to {result}?&quot;
 );

 return result;
 }
}
</code></pre>
Now, you might be thinking to yourself:
<blockquote>
Wait a minute. Since the consumer would need to construct the <code>MyService</code> object anyway, it still needs to know what <code>IEmailSender</code> should be used, regardless of whether it passes it via the <code>MyService</code> constructor or the <code>Add</code> method itself.
</blockquote>
Dependency injection is a recursive pattern. Just like how <code>IEmailSender</code> is injected into <code>MyService</code> instead of letting <code>MyService</code> create its own sender, your consumer will also get its <code>MyService</code> dependency injected, and it generally wouldn't be creating its own <code>MyService</code> instance.
Just as a quick example, you'd expect the same dependency injection pattern for your consumer:
<pre><code>public class MyConsumer
{
 private MyService _myService;

 public MyConsumer(MyService myService)
 {
 _myService = myService;
 }

 public int CountFingers()
 {
 var totalFingers = myService.Add(leftHand.Fingers, rightHand.Fingers);
 }
</code></pre>
Notice how the <code>CountFingers</code> method cares about how to add two numbers, but it doesn't care one bit about <code>IEmailSender</code> objects. <code>CountFingers</code> is only interested in using a (created) service, it's not interested in creating one.
If we had required <code>CountFingers</code> to have to pass the mail sender object as well, that would've significantly increased the complexity of the code, and the mail-sender-creating part of that code would've been a complete distraction from the true purpose of the method, i.e. counting the consumer's fingers.
<hr />
The reason I mentioned that your friend is mostly but not completely on track is that there are exceptions to this. His advice is generally correct but it's not universally true.
1
One example is pure functions. These are static functions who track no state, and have no side effect except the value they return.
<blockquote>
even if there is such a simple thing as a string helper
</blockquote>
Helper methods are often this exact kind of pure function. One C# example here is <code>String.Join</code>:
<pre><code>var numbers = new int[] { 1, 2, 3, 4, 5 };

var result = String.Join(&quot;, &quot;, numbers);

Console.WriteLine(result); // &quot;1, 2, 3, 4, 5&quot;
</code></pre>
Pure functions, by virtue of being pure, generally escape the requirement of being context-specific and therefore being considered as a dependency that must be injected.
Just to be clear, pure functions exist in a lot of code bases, but they are few and far between, usually nothing more than trivial helper methods that people tend to gloss over. The reason your friend's advice did not include this exception is possibly because the codebase he works in doesn't have pure functions
2
Another example of an exception to using constructor-based dependency injection is when you want the dependency to be passed as a method parameter, because the consumer very specifically cares about choosing this dependency.
For example, if you want to change the behavior of a method. Let's look at <code>OrderBy</code>, which sorts the elements of a collection based on a particular equality comparison.
<pre><code>var numbers = new int[] { 1, 4, 3, 2, 5 };

var orderedNumbers = numbers.OrderBy(x =&gt; x);
</code></pre>
By default, it uses the default comparison logic, which in the case of integers is a simple <code>a &lt; b</code> check. However, you are able to write your own comparer class, which uses a custom comparison logic. For example, you might want to sort numbers not by their size, but by how many factors you get when you factorize them.
<pre><code>var numbersOrderedByFactorization = numbers.OrderBy(x =&gt; x, new FactorizationComparer());
</code></pre>
By injecting this comparer via the method, the consumer is able to very directly control how the method behaves.
While having to inject this dependency via method parameter was considered an unjustified burden when we were discussing the mailsender example, in this case the ability to choose the comparer is desirable and actually something the consumer is interested in.
This is therefore a very contextual consideration whether your consumer will be interested in deciding this dependency or not. There is no universal answer here.

I'm working with services and I found out there are at least 3 ways to use them inside controllers...
Statically: Like helper, <code>Text::uppercase('foo')</code>
Instancing it: <code>$text = new Text(); $text-&gt;uppercase('foo');</code>
Injecting with reflection through parameters:
<pre><code>public function(Text $text) {
 $text-&gt;uppercase('foo');
}
</code></pre>
Injecting with reflection, but on the constructor:
<pre><code>private $text;
__construct(Text $text){
 $this-&gt;text = $text;
}

public function anyMethod() {
 $this-&gt;text-&gt;uppercase('foo');
}
</code></pre>
A friend of mine, who works for a lot of time with this, told me that is an error to use it in different ways, and that he always uses the constructor method, even if there is such a simple thing as a string helper.
I'm a bit confused about this. From the pure and strong theory, what is the best way to work on this pattern?
The reference I'm talking about:
<a href="https://blog.quickadminpanel.com/laravel-when-to-use-dependency-injection-services-and-static-methods/" rel="noreferrer">https://blog.quickadminpanel.com/laravel-when-to-use-dependency-injection-services-and-static-methods/</a>

Service Design Pattern

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

教程

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

腾讯云智能顾问专区

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AI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

功能1上新10个字符

功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符功能2描述100个字符。

功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符功能2上新100个字符。

功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符功能5描述100个字符

功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符功能5上新100个字符

功能4上新

文章&问答评论现已支持表情

全新交互，全新视觉，新增快捷键、悬浮工具栏、高亮块等功能并同时优化现有功能，全面提升创作效率和体验

社区富文本编辑器全新改版！诚邀体验～ 

精选全网热门MCP server，让你的AI更好用 🚀

💥开发者 MCP广场重磅上线！

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

聚焦“写作效率、视觉美观与运行性能”三方面进行全面升级，为您提供更高效、稳定的创作环境

社区富文本&Markdown编辑器全新改版上线，欢迎大家体验!

诚挚邀请您参与本次调研，分享您的真实使用感受与建议。您的反馈至关重要，感谢您的支持与参与！

社区新版编辑器体验调研

我在服务部门工作，我发现至少有3种方法可以在控制器内部使用.静态:像助手一样，Text::uppercase('foo')实例：$text = new Text(); $text->uppercase('foo');通过参数注入反射：public function(Text $text) {    $text->uppercase('foo');}注入反射，但在构造函数上：private $tex

问服务设计模式
EN

回答 1

Software Engineering用户

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

问服务设计模式EN