Post hooks

Post hooks

"Post" middelwares are defined the same way as "pre" middlewares. The main difference is that if you reject the Promise of your middleware because an error occured, the original method still resolves and a Symbol is added to the response containing the post hooks error(s).

// user.model.js

const schema = new Schema({ username: { ... }, ... });

// add "post" save middleware
schema.post('save', function postSave(){
    return new Promise((resolve, reject) => {
        const email = this.email;

        // ... do anything needed, maybe send an email?

        if (someError) {
            // If there is any error reject the Promise
            return reject({ code: 500, message: 'Houston something went wrong.' });
        }
    });
});

// ....

// user.controller.js

const gstore = require('gstore-node')();

const User = require('./user.model');
const user = new User({ name: 'John', email: '[e-mail]' });

user.save().then((entity) => {
    // You should do this check if you have post hooks that can fail
    if (entity[gstore.ERR_HOOKS]) {
        console.log(entity[gstore.ERR_HOOKS][0].message); // 'Houston something went wrong.'
    }
    ...    
});

Note The response from a "post" hook on delete() contains the key(s) of the entitie(s) deleted.

// key can be one Key or an Array of Keys deleted
userSchema.post('delete', function postDelete({ key }){
    ...
    return Promise.resolve();
});

You can also pass an Array of middleware to execute

function middleware1() {
    return Promise.resolve();
}

function middleware2() {
    return Promise.resolve();
}

userSchema.post('save', [middleware1, middleware2]);

Transactions and Post Hooks

When you save or delete an entity from inside a transaction, gstore adds an execPostHooks() method to the transaction instance. If the transaction succeeds and you have any post('save') or post('delete') hooks on any of the entities modified during the transaction you need to call this method to execute them.

const transaction = gstore.transaction();

transaction.run().then(() => {
    const user = new User({ name: 'john' });

    user.save(transaction);
    BlogPost.delete(123, null, null, transaction);

    transaction.commit()
        .then((data) => {
            transaction.execPostHooks() // execute "post" hooks
                .then(() => {
                    const apiResponse = data[0];
                    // all done!
                });
            });
});