Continuing from the previous article Singleton pattern of php pattern design, (although it doesn’t seem to have much to do with it) . Today we will talk about the second basic pattern design-factory pattern.
So what is factory mode?
Judging from the name, there seems to be no clue. Factory mode, related to production? Or is it related to the production process? Could it be related to the factory leaders? Is it related to the leadership secretary? Secretary... Okay, let’s not get too close. The so-called factory model is really related to production. What to produce? What is produced is an instance object. What equipment is used to produce it? Produced through a factory class. How to produce it? The factory class calls its own static method to produce object instances.
The factory pattern has a key construct, which is a static method named Factory according to the general principle. However, this is just a principle. Although the factory method can name this static method arbitrarily, it can also accept parameters of any data and must return a object.
Why use factory mode?
Many people who have never been exposed to the factory pattern can’t help but ask, why do I have to spend so much effort constructing a factory class to create objects? Instead of applying things like easy maintenance and scalability, we can consider such a simple problem. If in the project, we create objects through a class. When it is almost completed or has been completed and the function needs to be extended, it is found that the original class name is not very suitable or that the class needs to add constructor parameters to achieve function expansion. Holy shit! I have created a lot of object instances through this class. Do I still have to change them one by one? Only now do we feel the breadth and depth of "high cohesion and low coupling". No problem, factory methods can solve this problem.
Think about it again, I want to connect to the database, there are several methods in php, mysql extension, mysqli extension, PDO extension. I just want an object for future operations. Which one I want depends on the situation. Since you are all connecting to the database, you should have the same functionality, establishing connections, querying, disconnecting... (the importance of interfaces is shown here). All in all, these methods should be "united and united to the outside world." How to achieve this? Take advantage of the factory pattern.
How to implement the factory pattern?
Compared to the singleton mode, we have provided enough information above, the factory class, and the static methods in the factory class. Just new the object instance that needs to be created in the static method. Of course, as for the second question above, we can simply make a judgment based on the parameters of the static method of the factory class. Regardless of whether you use if..else.. or switch..case.., it would be nice to be able to quickly and efficiently complete the work of determining which class to create. Finally, be sure to remember that factory class static methods return an object. Not two, let alone three.
Basic factory class:
<span>//</span><span>要创建对象实例的类</span>
<span>class</span><span> MyObject{
}
</span><span>//</span><span>工厂类</span>
<span>class</span><span> MyFactory{
</span><span>public</span> <span>static</span> <span>function</span><span> factory(){
</span><span>return</span> <span>new</span> MyObject():<span>
}
}
</span><span>$instance</span>=MyFactory::factory();A slightly more complex factory pattern:
<?<span>php
</span><span>interface</span><span> Transport{
</span><span>public</span> <span>function</span><span> go();
}
</span><span>class</span> Bus <span>implements</span><span> Transport{
</span><span>public</span> <span>function</span><span> go(){
</span><span>echo</span> "bus每一站都要停"<span>;
}
}
</span><span>class</span> Car <span>implements</span><span> Transport{
</span><span>public</span> <span>function</span><span> go(){
</span><span>echo</span> "car跑的飞快"<span>;
}
}
</span><span>class</span> Bike <span>implements</span><span> Transport{
</span><span>public</span> <span>function</span><span> go(){
</span><span>echo</span> "bike比较慢"<span>;
}
}
</span><span>class</span><span> transFactory{
</span><span>public</span> <span>static</span> <span>function</span> factory(<span>$transport</span><span>)
{
</span><span>switch</span> (<span>$transport</span><span>) {
</span><span>case</span> 'bus':
<span>return</span> <span>new</span><span> Bus();
</span><span>break</span><span>;
</span><span>case</span> 'car':
<span>return</span> <span>new</span><span> Car();
</span><span>break</span><span>;
</span><span>case</span> 'bike':
<span>return</span> <span>new</span><span> Bike();
</span><span>break</span><span>;
}
}
}
</span><span>$transport</span>=transFactory::factory('car'<span>);
</span><span>$transport</span>->go();When you need the factory static method to be factory(), don’t foolishly name the factory class Factory. Why? Don’t forget about the constructor with the same name~
Finally, let’s talk about some feelings. Many newbies are more ambitious than others. They have just learned if..else.., session, and cookie and are about to learn something advanced. When talking to people, they often talk about scalability, maintainability and so on. As for examples, you will be speechless for a while. Sometimes I feel that no matter whether I write code or study with others, I am always in the stage of "searching for others in the crowd". After really studying hard, I suddenly look back and realize, "That person is in the dim light" and exclaim: "It turns out that this person is..." It’s just ***.”
I dare not admit that I know how to design patterns. I am also a beginner for less than a year. I only want to share my blog to record my learning process. I want to know more about it. If it can help others, that would be even better~~~
Series of articles:
PHP pattern design singleton pattern
PHP pattern design factory pattern
PHP pattern design registration tree pattern
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