tachybase_todo/docs/en-US/api/resourcer/middleware.md

Middleware

It is similar to the middleware of Koa, but with more enhanced features for easy extensions.

The defined middleware can be inserted for use in multiple places, such as the resourcer, and it is up to the developer for when to invoke it.

Constructor

Signature

• constructor(options: Function)
• constructor(options: MiddlewareOptions)

Parameter

Name	Type	Default	Description
options	Function	-	Handler function of middlware
options	MiddlewareOptions	-	Configuration items of middlware
options.only	string[]	-	Only the specified actions are allowed
options.except	string[]	-	The specified actions are excluded
options.handler	Function	-	Handler function

Example

Simple definition:

const middleware = new Middleware((ctx, next) => {
  await next();
});

Definition with relevant parameters:

const middleware = new Middleware({
  only: ['create', 'update'],
  async handler(ctx, next) {
    await next();
  },
});

Instance Methods

getHandler()

Get the orchestrated handler functions.

Example

The following middleware will output 1 and then 2 when requested.

const middleware = new Middleware((ctx, next) => {
  console.log(1);
  await next();
});

middleware.use(async (ctx, next) => {
  console.log(2);
  await next();
});

app.resourcer.use(middleware.getHandler());

use()

Add a middleware function to the current middleware. Used to provide extension points for the middleware. See getHandler() for the examples.

Signature

• use(middleware: Function)

Parameter

Name	Type	Default	Description
middleware	Function	-	Handler function of the middleware

disuse()

Remove the middleware functions that have been added to the current middleware.

Signature

• disuse(middleware: Function)

Parameter

Name	Type	Default	Description
middleware	Function	-	Handler function of the middleware

Example

The following example will only output 1 when requested, the output of 2 in fn1 will not be executed.

const middleware = new Middleware((ctx, next) => {
  console.log(1);
  await next();
});

async function fn1(ctx, next) {
  console.log(2);
  await next();
}

middleware.use(fn1);

app.resourcer.use(middleware.getHandler());

middleware.disuse(fn1);

canAccess()

Check whether the current middleware is to be invoked for a specific action, it is usually handled by the resourcer internally.

Signature

• canAccess(name: string): boolean

Parameter

Name	Type	Default	Description
name	string	-	Name of the action

Other Exports

branch()

Create a branch middleware for branching in the middleware.

Signature

• branch(map: { [key: string]: Function }, reducer: Function, options): Function

Parameter

Name	Type	Default	Description
map	{ [key: string]: Function }	-	Mapping table of the branch handler function, key names are given by subsequent calculation functions when called
reducer	(ctx) => string	-	Calculation function, it is used to calculate the key name of the branch based on the context
options?	Object	-	Configuration items of the branch
options.keyNotFound?	Function	ctx.throw(404)	Handler function when key name is not found
options.handlerNotSet?	Function	ctx.throw(404)	The function when no handler function is defined

Example

When authenticating user, determine what to do next according to the value of the authenticator parameter in the query section of the request URL.

app.resourcer.use(branch({
  'password': async (ctx, next) => {
    // ...
  },
  'sms': async (ctx, next) => {
    // ...
  },
}, (ctx) => {
  return ctx.action.params.authenticator ?? 'password';
}));