AirMVVM

AirMVVM.Commands

This library includes some useful mvvm commands.

SingleExecutionCommand

This command will executed once.

// ViewModel part
viewModel.SaveCommand = new SingleExecutionCommand(async () =>
                                        {
                                            await Save();
                                        });
BindingContext = viewModel;

// View
<Button Text="SaveText" Command="{Binding SaveCommand}" />

// Behaviour
After click button will be disabled. Command will executed once.

SequentialСommand

This command may be invoked multiple times. But at one time, the command can be executed once. SequentialСommand may be useful for prevent double click problems.

// ViewModel part
viewModel.SaveCommand = new SingleExecutionCommand(async (commandFinishedCallback) =>
                                        {
                                            await Save();
                                            commandFinishedCallback();
                                        });
BindingContext = viewModel;

// View
<Button Text="SaveText" Command="{Binding SaveCommand}" />

// Behaviour
After click button will be disabled. After command execution button will be enabled again.

RelayCommand

This command can raises CanExecuteChanged event and transfers information between execute action and canExecute predicate over dictionary storage.

// ViewModel part
viewModel.SaveCommand = new RelayCommand(
                                async (self, param) =>
                                {
                                    self.Storage["IsStarted"] = true;
                                    self.RaiseCanExecuteChanged();
                                    await Save(param);
                                    self.Storage.Clear();
                                    self.RaiseCanExecuteChanged();
                                }, 
                                (self, param) =>
                                {
                                    return !self.Storage.ContainsKey("IsStarted") && customPredicate(param);
                                });
BindingContext = viewModel;

// View
<Button Text="SaveText" Command="{Binding SaveCommand}" />

// Behaviour
After click button will be disabled. After command execution button will be enabled again.

License

Copyright (c) Viridovics

Licensed under the MIT License.