parkes-presenter

Simple, flexible JSON presentation methods for sequelize

Useful in situations when a separate presentation layer or views would be overkill. Supports hiding internal ids and mapping them to external keys and creating the appropriate foreign keys.

Getting Started

Presenter.extendModels(sequelize.models, {
  presentationKey: 'uuid', // default
});

Post = sequelize.define('post', { ... });

Post.publicAttributes = ['title', 'body', 'userUuid'];
Post.nestedModels = ['comments'];

post = await Post.findOne();

post.toPublic();

// Will yield something like
{
  title: 'My Post',
  body: 'This is my post',
  userUuid: 'uuid_for_user',
  comments: {
    [
      comment1.toPublic(),
    ]
  }
}

Methods

Assing parkes-presenter adds 3 methods to instances of your models

presentJson(permittedAttributes, { include, includeMethod })

permittedAttributes the attributes to copy from the model, if these end in the name of your presentation key (eg postUuid), a virtual foreign include array of model names to include when creating JSON includeMethod method to call on nested models to generate their JSON

toPublic

calls presentJson with the class's publicAttributes and nestedModels

toPrivate

Alternate presenter that uses privateAttributes and nestedModels.private

Lazy Loading

By default, parkes-presenter will lazy load any missing associations.

To prevent infinite recursion, it will not repeat a nested model.

This does come at a performance cost. To improve performance you may want to eager load associations before passing them in.

You can disable lazy loading by setting the missingAssociations option. It can be set to either false, 'warn' or 'load'.

'load' enables the default behaviour of lazy loading.

If set to false then associations (and foreign keys) will only be present if they have been eager loaded from sequelize (or if you manually add them to the record).

Setting warn will cause console warnings when expected associations are missing.

This can get pretty noisy, so you can also pass in an object specifying 'warn' or 'load' for each model name.

Presenter.extendModels(sequelize.models, {
  missingAssociations: {
    post: 'warn',
    user: 'load',
    comment: 'false'
  }
});

Eager Loading

To eager load associations use the include option. You should also use duplicating: false where possible (eg belongsTo and hasOne associations) to improve query performance.

User.findOne({ include: [
    { model: Post, as: 'posts' },
    { model: Team, as: 'team', duplicating: false },
  ]
})

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