thinkphp Development Framework function Detailed: D method

D method

D method should be used more methods, used to instantiate the custom model class, is a thinkphp framework for the model class instantiation of a package, and implemented a singleton mode, support cross project and group calls, the call format is as follows:
D (' [Project://][Group/] model ', ' model layer name ')
The return value of the method is the instantiated model object.

The D method can automatically detect the model class and, if there is a custom model class, instantiate the custom model class and, if it does not, instantiate the model base class and not repeat the instantiated models.
The most common use of the D method is to instantiate a custom model for the current project, for example:

Imports the lib/model/usermodel.class.php file under the current project and then instantiates the Usermodel class, so the actual code might be equivalent to the following:

However, if the D method is used, if the Usermodel class does not exist, it is automatically invoked

And the second call does not need to be instantiated again to reduce the cost of a certain object instantiation.
The D method can support cross grouping and project instantiation models, for example:

Note: To implement a cross project invocation model, you must ensure that the directory structure of the two projects is tied.

Starting with version 3.1, the D method can also instantiate other models because of increased support for layered models, such as:

is imported and instantiated, equivalent to the following code: lib/service/userservice.class.php