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loopback-connector-hooks(3) - Hooks and object lifecycle.

DESCRIPTION

Hook is a class method called on object when some event happens. List of events:

initialize: Called after new Model called.
create: Called before and after create.
update: Called before and after save (except create).
save: Called before and after save (including both create and update).
validate: Called before and after validations.
destroy: Called before and after destroy on instance.

Each hook except initialize accepts callback as the first argument. This callback should be called when hook is done. All hooks are called on object instance, but it's not recommended to use this for updating all hooks where data argument is available (second argument for all data-related before-hooks: save, update, create).

INITIALIZE

Initialize hook called when new object created after all setters and defaults being applied.

Model.afterInitialize = function() {
    this.property = 'some value;
    console.log('afterInitialize called');
};
new Model; // afterInitialize called

CREATE

Create hooks is being called when object is created. The beforeCreate hook accepts data as a second argument.

Model.beforeCreate = function(next, data) {
    // use data argument to update object
    data.createdAt = new Date();
    console.log('before');
    next();
};

Model.afterCreate = function(next) {
    this.notifySocialNetworks();
    this.sendEmailNotifications();
    console.log('after');
    next();
};

Model.create({foo: 'bar'}, function(err, model) {
    console.log('callback');
});

Example output will be:

before
after
callback

UPDATE

Update hooks called on each save except create. The beforeUpdate hook accepts data as second argument. The data argument contains only actual data for update, not full object data.

Model.beforeUpdate = function(next, data) {
    // use data argument to update object
    // in update hook data argumen only contains data for update (not
    // full object)
    data.updatedAt = new Date();
    console.log('before');
    next();
};

Model.afterUpdate = function(next) {
    this.scheduleFulltextIndexUpdate();
    console.log('after');
    next();
};

model.updateAttributes({foo: 'bar'}, function(err, model) {
    console.log('callback');
});

Example output will be:

before
after
callback

SAVE

Save hooks called on each save, both during update and create. The beforeSave hook accepts data as a second argument. For this cook hook data argument is the same as this when model.save() is called. When model.updateAttributes() called data argument contains only actual changes.

Model.beforeSave = function(next, data) {
    if ('string' !== typeof data.tags) {
        data.tags = JSON.stringify(data.tags);
    }
    next();
};

Model.afterSave = function(next) {
    next();
};

DESTROY

Hook is destroyed once model.destroy() is called. Please note that destroyAll method doesn't call destroy hooks.

VALIDATE

Validate hooks called before and after validation and should be used for data modification and not for validation. Use custom validation described in loopback-connector-validations(3) man section.

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