Support for typed "this" in lifecycle methods (created, started, stopped)

[marceliwac]

Hi, at the moment it seems like there is no way to override the type for this parameter for the lifecycle methods (created , started and stopped). In consequence, it's impossible to create those methods if they implement a custom this (similarly to how methods and actions do it).

This can be temporarily ignored as suggested in #67, but that's a workaround and not a fix.

I'm realtively new to typescript so I might be missing some obvious solution / best practices related to this, but I think the following could work:

index.d.ts

// ...

type ServiceSyncLifecycleHandler<S = ServiceSettingSchema> = (this: Service<S>) => void;
type ServiceAsyncLifecycleHandler<S = ServiceSettingSchema> = (this: Service<S>) => void | Promise<void>;

interface ServiceSchema<S = ServiceSettingSchema> {
	name: string;
	version?: string | number;
	settings?: S;
	dependencies?: string | ServiceDependency | (string | ServiceDependency)[];
	metadata?: any;
	actions?: ServiceActionsSchema;
	mixins?: Partial<ServiceSchema>[];
	methods?: ServiceMethods;
	hooks?: ServiceHooks;

	events?: ServiceEvents;
	created?: ServiceSyncLifecycleHandler<S> | ServiceSyncLifecycleHandler<S>[];
	started?: ServiceAsyncLifecycleHandler<S> | ServiceAsyncLifecycleHandler<S>[];
	stopped?: ServiceAsyncLifecycleHandler<S> | ServiceAsyncLifecycleHandler<S>[];

	[name: string]: any;
}

// ...

should be changed to:

index.d.ts

// ...

type ServiceSyncLifecycleHandler<S = ServiceSettingsSchema, T = Service<S>> = (this: T) => void;
type ServiceAsyncLifecycleHandler<S = ServiceSettingSchema, T = Service<S>> = (this: T) => void | Promise<void>;


interface ServiceSchema<S = ServiceSettingSchema, T = void> {
	name: string;
	version?: string | number;
	settings?: S;
	dependencies?: string | ServiceDependency | (string | ServiceDependency)[];
	metadata?: any;
	actions?: ServiceActionsSchema;
	mixins?: Partial<ServiceSchema>[];
	methods?: ServiceMethods;
	hooks?: ServiceHooks;

	events?: ServiceEvents;
	created?: ServiceSyncLifecycleHandler<S, T> | ServiceSyncLifecycleHandler<S, T>[];
	started?: ServiceAsyncLifecycleHandler<S, T> | ServiceAsyncLifecycleHandler<S, T>[];
	stopped?: ServiceAsyncLifecycleHandler<S, T> | ServiceAsyncLifecycleHandler<S, T>[];

	[name: string]: any;
}

// ...

The above code is meant to provide a way to supply additional type for this parameter at the service declaration level (e.g. in greeter.service.ts), which would change it from:

export interface GreeterSettings extends ServiceSettingSchema {
	defaultName: string;
}

export interface GreeterMethods {
	uppercase(str: string): string;
}

export type GreeterThis = Service<GreeterSettings> & GreeterMethods;

const GreeterService: ServiceSchema<GreeterSettings> = {
	name: "greeter",
	settings: {
		defaultName: "Moleculer",
	},
	dependencies: [],
	actions: {},
	events: {},
	methods: {
		uppercase(str: string) {
			return str.toUpperCase()();
                 },
	},
	created(this: GreeterThis) {	 		//  <--  This does not work
		console.log(this.broker.services);
	},

	async started(this: GreeterThis){ 	 	//  <--  This does not work
		this.uppercase('hello world');
	},

	async started(this: GreeterThis){  		//  <--  This does not work
		this.uppercase('goodbye world');
	},
};

to

export interface GreeterSettings extends ServiceSettingSchema {
	defaultName: string;
}

export interface GreeterMethods {
	uppercase(str: string): string;
}

export type GreeterThis = Service<GreeterSettings> & GreeterMethods;

const GreeterService: ServiceSchema<GreeterSettings, GreeterThis> = {	//  <--  This is the actual change
									//       in service declaration
	name: "greeter",
	settings: {
		defaultName: "Moleculer",
	},
	dependencies: [],
	actions: {},
	events: {},
	methods: {
		uppercase(str: string) {
			return str.toUpperCase()();
                 },
	},
	created(this: GreeterThis) {
		console.log(this.broker.services);
	},

	async started(this: GreeterThis){
		this.uppercase('hello world');
	},

	async started(this: GreeterThis){
		this.uppercase('goodbye world');
	},
};

Please let me know if you'd like me to create a PR with this change.

[icebob]

Ok, plz create a PR and we can discuss your suggestion with other TS guys.

[marceliwac]

@icebob I've just realised the type defs are in the other repository, I hope that's not a problem. It should now be cross-referenced.