Command Contracts

Core command support in @cratis/arc is built around typed command classes generated from backend command definitions.

ICommand

The core command interface provides execution and state-management capabilities:

interface ICommand<TCommandContent = object, TCommandResponse = object> extends ICanBeConfigured {
    readonly route: string;
    readonly roles: string[];
    readonly propertyDescriptors: PropertyDescriptor[];
    execute(
        allowedSeverity?: ValidationResultSeverity,
        ignoreWarnings?: boolean
    ): Promise<CommandResult<TCommandResponse>>;
    validate(): Promise<CommandResult<TCommandResponse>>;
    validateClientSide(): CommandResult<TCommandResponse>;
    clear(): void;
    setInitialValues(values: TCommandContent): void;
    setInitialValuesFromCurrentValues(): void;
    revertChanges(): void;
    readonly hasChanges: boolean;
    propertyChanged(property: string): void;
    onPropertyChanged(callback: PropertyChanged, thisArg: object): void;
}

Change Tracking

Commands track property changes automatically.

• hasChanges indicates whether current values differ from the baseline.
• setInitialValues() sets an explicit baseline.
• setInitialValuesFromCurrentValues() currently snapshots truthy values only. Completed server executions call it even on unsuccessful results; see baseline limitations.
• revertChanges() restores baseline values.
• validate() can return a local validation failure before reaching the server. When reached, server preflight runs filters without executing the handler; validateClientSide() never calls the server.

Property Change Notifications

Commands expose property-change callbacks for reactive flows:

// Illustrative fragment: retain this owner while notifications are needed.
const owner = {
    onChanged(property: string) {
        console.log(`Property ${property} changed`);
    }
};
command.onPropertyChanged(owner.onChanged, owner);

The callback and its receiver are weakly referenced. Supply the required receiver and retain both it and the callback for the subscription’s intended lifetime; an otherwise unreferenced inline function is not a durable listener.

See Also

• Validation And Results
• Configuration
• React Commands