Gate

Gate Class

The Gate class in Vania allows you to manage and define authorization logic for your Dart application. It provides a mechanism to determine if a user is authorized to perform specific actions based on defined abilities. gates are defined within the boot method of the app\providers\app_service_provider.dart class

info

If you don't already have the app_service_provider.dart class, you can create one using the CLI command vania make:provider

Methods

1. define()

The define() method allows you to define a new ability. Each ability is represented by a closure (function) that contains the logic to determine if a user can perform a specific action.

Usage:

Gate().define('canDeletePost', () {
  return user.id == post.userId;
});

• Parameters:

  • ability (String): The name of the ability.
  • callback (Function): A closure that contains the authorization logic. This function should return true if the user is authorized and false otherwise.

• Example:

Gate().define('canUpdatePost', () {
  return user.id == post.userId;
});

2. allows()

The allows() method is used to determine if the current user is allowed to perform a given action based on a defined ability.

Usage:

bool canDelete = Gate().allows('canDeletePost');

• Parameters:

  • ability (String): The name of the ability to check.

• Returns: true if the ability is allowed (the closure returns true), otherwise false.

• Example:

if (Gate().allows('canUpdatePost')) {
  // The user can update the post
} else {
  // The user is not authorized to update the post
}

3. denies()

The denies() method checks if the user is explicitly denied an action based on the ability. It returns true if the action is denied (i.e., if allows() returns false).

Usage:

bool cannotDelete = Gate().denies('canDeletePost');

• Parameters:

  • ability (String): The name of the ability to check.

• Returns: true if the ability is denied (the closure returns false), otherwise false.

• Example:

if (Gate().denies('canUpdatePost')) {
  // The user is not authorized to update the post
} else {
  // The user can update the post
}

4. has()

The has() method determines if a given ability has been defined. This is useful for checking whether a specific ability is available before attempting to authorize an action.

Usage:

bool hasAbility = Gate().has('canDeletePost');

• Parameters:

  • ability (String): The name of the ability to check.

• Returns: true if the ability is defined, otherwise false.

• Example:

if (Gate().has('canUpdatePost')) {
  print('The ability to update posts is defined.');
} else {
  print('The ability to update posts is not defined.');
}

5. can()

The can() method is a helper function that checks if an ability is allowed. It simplifies the usage of the allows() method.

Usage:

bool canUpdate = can('canUpdatePost');

• Parameters:

  • ability (String): The name of the ability to check.

• Returns: true if the ability is allowed (the closure returns true), otherwise false.

• Example:

if (can('canUpdatePost')) {
  print('User can update the post.');
}

6. cannot()

The cannot() method is a helper function that checks if an ability is denied. It simplifies the usage of the denies() method.

Usage:

bool cannotUpdate = cannot('canUpdatePost');

• Parameters:

  • ability (String): The name of the ability to check.

• Returns: true if the ability is denied (the closure returns false), otherwise false.

• Example:

if (cannot('canUpdatePost')) {
  print('User cannot update the post.');
}

Example Usage

Here is an example of how to use the Gate class to define and check authorization logic:

void main() {
  var user = User(id: 1, isAdmin: false);
  var post = Post(id: 1, userId: 1);

  // Define a gate to check if the user can update the post
  Gate().define('canUpdatePost', () {
    return user.id == post.userId;
  });

  // Check if the user can update the post
  if (Gate().allows('canUpdatePost')) {
    print('User is authorized to update the post.');
  } else {
    print('User is not authorized to update the post.');
  }

  // Use helper methods for authorization checks
  if (can('canUpdatePost')) {
    print('User can update the post.');
  }

  if (cannot('canUpdatePost')) {
    print('User cannot update the post.');
  }

  // Check if the ability to update the post exists
  if (Gate().has('canUpdatePost')) {
    print('The update post ability is defined.');
  }
}