index.js

const _ = require('lodash')

function getVirtual(model, virtualName, ...virtuals) {
  if (model.virtuals && typeof model.virtuals === 'object' && model.virtuals[virtualName]) {
    return model.virtuals[virtualName].get
      ? model.virtuals[virtualName].get.apply(model, virtuals)
      : model.virtuals[virtualName].apply(model, virtuals)
  }
}

function getVirtuals(model, params) {
  const attrs = {}
  if (model.virtuals != null) {
    for (const virtualName in model.virtuals) {
      const paramsForVirtual = typeof params === 'object' && params !== null ? params[virtualName] : undefined
      attrs[virtualName] = getVirtual(model, virtualName, paramsForVirtual)
    }
  }
  return attrs
}

function setVirtual(value, key) {
  const virtual = this.virtuals && this.virtuals[key]
  if (virtual) {
    if (virtual.set) virtual.set.call(this, value)
    return true
  }
}

// Virtuals Plugin
// Allows getting/setting virtual (computed) properties on model instances.
// -----
module.exports = (bookshelf) => {
  const proto = bookshelf.Model.prototype
  const Model = bookshelf.Model.extend({
    outputVirtuals: true,

    // If virtual properties have been defined they will be created
    // as simple getters on the model.
    constructor(attributes, options) {
      proto.constructor.apply(this, arguments)
      const virtuals = this.virtuals
      if (virtuals && typeof virtuals === 'object') {
        for (const virtualName in virtuals) {
          let getter, setter
          if (virtuals[virtualName].get) {
            getter = virtuals[virtualName].get
            setter = virtuals[virtualName].set ? virtuals[virtualName].set : undefined
          } else {
            getter = virtuals[virtualName]
          }
          Object.defineProperty(this, virtualName, {
            enumerable: true,
            get: getter,
            set: setter
          })
        }
      }
    },

    // Passing `{virtuals: true}` or `{virtuals: false}` in the `options`
    // controls including virtuals on function-level and overrides the
    // model-level setting
    toJSON(options) {
      let attrs = proto.toJSON.call(this, options)
      if (options && options.omitNew && this.isNew()) {
        return attrs
      }
      if (!options || options.virtuals !== false) {
        if ((options && options.virtuals === true) || this.outputVirtuals) {
          attrs = Object.assign(attrs, getVirtuals(this, options && options.virtualParams))
        }
      }
      return attrs
    },

    // Allow virtuals to be fetched like normal properties
    get(attr) {
      if (this.virtuals && typeof this.virtuals === 'object' && this.virtuals[attr]) {
        return getVirtual.apply(undefined, [this, attr].concat(Array.from(arguments).slice(1)))
      }
      return proto.get.apply(this, arguments)
    },

    // Allow virtuals to be set like normal properties
    set(key, value, options) {
      if (!key) return this

      // Determine whether we're in the middle of a patch operation based on the
      // existence of the `patchAttributes` object.
      const isPatching = this.patchAttributes != null

      // Handle `{key: value}` style arguments.
      if (key && typeof key === 'object') {
        const nonVirtuals = _.omitBy(key, setVirtual.bind(this))
        if (isPatching) {
          Object.assign(this.patchAttributes, nonVirtuals)
        }
        // Set the non-virtual attributes as normal.
        return proto.set.call(this, nonVirtuals, options)
      }

      // Handle `"key", value` style arguments for virtual setter.
      if (setVirtual.call(this, value, key)) {
        return this
      }

      // Handle `"key", value` style assignment call to be added to patching
      // attributes if set("key", value, ...) called from inside a virtual setter.
      if (isPatching) {
        this.patchAttributes[key] = value
      }

      return proto.set.apply(this, arguments)
    },

    // Override `save` to keep track of state while doing a `patch` operation.
    save(key, value, options) {
      let attrs = {}

      // Handle both `"key", value` and `{key: value}` -style arguments.
      if (key == null || typeof key === 'object') {
        attrs = key && _.clone(key)
        options = _.clone(value) || {}
      } else {
        attrs[key] = value
        options = options ? _.clone(options) : {}
      }

      // Determine whether to save using update or insert
      options.method = this.saveMethod(options)

      // Check if we're going to do a patch, in which case deal with virtuals now.
      if (options.method === 'update' && options.patch) {
        // Extend the model state to collect side effects from the virtual setter
        // callback. If `set` is called, this object will be updated in addition
        // to the normal `attributes` object.
        this.patchAttributes = {}

        // Any setter could throw. We need to reject `save` if they do.
        try {
          // Check if any of the patch attributes are virtuals. If so call their setter. Any setter that calls
          // `this.set` will be modifying `this.patchAttributes` instead of `this.attributes`.
          for (const attributeName in attrs) {
            if (setVirtual.call(this, attrs[attributeName], attributeName)) {
              // This was a virtual, so remove it from the attributes to be passed to `Model.save`.
              delete attrs[attributeName]
            }
          }

          // Now add any changes that occurred during the update.
          Object.assign(attrs, this.patchAttributes)
        } catch (e) {
          return Promise.reject(e)
        } finally {
          // Delete the temporary object.
          delete this.patchAttributes
        }
      }

      return proto.save.call(this, attrs, options)
    }
  })

  // Lodash methods that we want to implement on the Model.
  const modelMethods = ['keys', 'values', 'toPairs', 'invert', 'pick', 'omit']

  // Mix in each Lodash method as a proxy to `Model#attributes`.
  modelMethods.forEach((method) => {
    Model.prototype[method] = function () {
      return _[method].apply(_, [Object.assign({}, this.attributes, getVirtuals(this))].concat(Array.from(arguments)))
    }
  })

  bookshelf.Model = Model
}