# MooseApp Base Class

-   Every MOOSE application contains a `MooseApp`-derived class.
-   The `MooseApp` contains:
    - Factories where application objects are built.
    - Warehouses where application objects are stored.
-   `MooseApp` objects can be combined (coupled) together to form larger simulations, see the `MultiApp` discussion.
-   `MooseApp` objects specialize the `validParams()` function.
- Parameters for MooseApps are read from the command line via:
    -   `InputParameters::addRequiredCommandLineParam()`
    -   `InputParameters::addCommandLineParam()`

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# Your AnimalApp.h/.C

- Your application's `MooseApp`-derived class must implement several important static functions:
    - `registerApps()`
    - `registerObjects()`
    - `associateSyntax()` (optional)
- The `MooseApp` is a convenient place to see the other applications and objects a given application depends on. 

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# Object Registration

-   The `MooseApp` object calls its own `registerObjects()` function and those of applications to which it is coupled. 
    - This is where you register all of the objects created in your application.
    - Typically done in the constructor.
- Strong coupling to other applications is implemented by calling the `registerObjects()` functions of other applications (also done in the constructor).
    - This makes the other application's objects available in your application.
- Newly-created applications (via `Stork`) register all MOOSE and MOOSE module objects by default.

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# main.C

- Every MOOSE application has a `main()` program, typically located in `src/main.C`.
- By default, a MOOSE application's `main()` program only does a few very specific things:
    - Calls `MooseInit()`
    - Calls `YourApp::registerApps()`
    - Builds your application object
    - Runs your application object
    - Deletes your application object
- See main.C in Example 1
- While it is possible to add additional code in `main()`, it's not recommended.