json

//[doc-seo]
{
    "Description": "Learn how to implement a simple state checking system in your applications to dynamically enable or disable objects based on conditions."
}

Simple State Checker

The simple state checking system can be used to enable/disable an object based on some dynamic conditions. For example, you can disable a menu item on the user interface, if the current user has not granted for a given permission. The simple state checking system provides a generic way to define and check such conditions.

Definition state checker.

Any class can inherit IHasSimpleStateCheckers to support state checks.

csharp

public class MyObject : IHasSimpleStateCheckers<MyObject>
{
    public int Id { get; set; }

    public List<ISimpleStateChecker<MyObject>> StateCheckers { get; }

    public MyObject()
    {
        StateCheckers = new List<ISimpleStateChecker<MyObject>>();
    }
}

The MyObject class contains a collection of state checkers, you can add your custom checkers to it.

csharp

public class MyObjectStateChecker : ISimpleStateChecker<MyObject>
{
    public Task<bool> IsEnabledAsync(SimpleStateCheckerContext<MyObject> context)
    {
        var currentUser = context.ServiceProvider.GetRequiredService<ICurrentUser>();
        return Task.FromResult(currentUser.IsInRole("Admin"));
    }
}

csharp

var myobj = new MyObject()
{
    Id = 100
};

myobj.SimpleStateCheckers.Add(new MyObjectStateChecker());

Definition Global State Checkers

AbpSimpleStateCheckerOptions is the options class that used to set the global state checkers for specific object.

Example: Add global state for MyObject:

csharp

services.Configure<AbpSimpleStateCheckerOptions<MyObject>>(options =>
{
    options.GlobalSimpleStateCheckers.Add<MyGlobalObjectStateChecker>();
    //options.GlobalSimpleStateCheckers.Add<>(); //Add more global state checkers
});

Write this inside the ConfigureServices method of your module.

Check the state

You can inject ISimpleStateCheckerManager<MyObject> service to check state.

csharp

bool enabled = await stateCheckerManager.IsEnabledAsync(myobj);

Batch check the states

If there are many instance items that require state checking, there may be performance problems.

In this case, you can implement ISimpleBatchStateChecker. It can check multiple items at once. You need to make sure that the same ISimpleBatchStateChecker instance is added to the SimpleStateCheckers of multiple instances.

SimpleBatchStateCheckerBase inherits the ISimpleBatchStateChecker interface and implements the IsEnabledAsync method of a single object by default.

csharp

public class MyObjectBatchStateChecker : SimpleBatchStateCheckerBase<MyObject>
{
    public override Task<SimpleStateCheckerResult<MyObject>> IsEnabledAsync(SimpleBatchStateCheckerContext<MyObject> context)
    {
        var result = new SimpleStateCheckerResult<MyObject>(context.States);

        foreach (var myObject in context.States)
        {
            if (myObject.Id > 100)
            {
                result[myObject] = true;
            }
        }

        return Task.FromResult(result);
    }
}

csharp

var myobj1 = new MyObject()
{
    Id = 100
};
var myobj2 = new MyObject()
{
    Id = 99
};

var myObjectBatchStateChecker = new MyObjectBatchStateChecker();

myobj1.SimpleStateCheckers.Add(myObjectBatchStateChecker);
myobj2.SimpleStateCheckers.Add(myObjectBatchStateChecker);

SimpleStateCheckerResult<MyObject> stateCheckerResult = await stateCheckerManager.IsEnabledAsync(new []{ myobj1, myobj2 });

Built-in State Checkers

The PermissionDefinition, ApplicationMenuItem and ToolbarItem objects have implemented state checks and have built-in general state checkers, you can directly use their extension methods.

csharp

RequireAuthenticated();
RequirePermissions(bool requiresAll, params string[] permissions);
RequireFeatures(bool requiresAll, params string[] features);
RequireGlobalFeatures(bool requiresAll, params Type[] globalFeatures);