Factory

This library creates a flexible Factory object.

Installation

npm install --save @leverege/factory

Usage

Include the library in your module:

const Factory = require( '@leverege/factory' )

const f = new Factory()
// Register your types
f.add( 'myType', MyTypeMsg )
f.add( 'myOtherType', MyOtherTypeMsg )

const json = { type : 'myOtherType', value : 5 }
const msg = f.create( json )

// At this point msg was created by calling new MyOtherMsg( json ) if MyOtherMsg
// is a Class, otherwise it is the result of MyOtherMsg( json )

The Factory.create() method can take multiple arguments, depending on your particular factory needs. If can be invoked with an object as shown above, or with a the type string directly with extra arguments:

const f = new Factory( Factory.ARGS )
f.add( 'someMsg', SomeMsg )
const msg = f.create( 'someMsg', param1, param2 )

Options

You can create a factory by calling new Factory( strategy ) or new Factory( options ) where the options are defined as

OptionDefaultDescription
name'Factory'Name used in errors
typeKey'type'The field name used when extracting the lookup type from an object
registrynullMap of type to object. This is like calling add() with key/value
defaultObjectnullDefault object to used if none is registered for the type
strategyFactory.AllThe creation strategy

Strategies

There are several different strategies for creating the resulting object, and you can write your own, if needed.

Factory.All

This is the default strategy. It will pass all arguments given to create() into the Class/function. So, assuming json.type maps to a Clazz.

f.create( json ) invokes new Clazz( json )
f.create( json, 'hello' ) invokes new Clazz( json, 'hello' )
f.create( json, 'hello', props ) invokes new Clazz( json, 'hello', props )

Factory.ARGS

This strategy would normally be used when the type and data to process aren't contained in the same object. It will pass all arguments given to create() after the type into the Class/function.

f.create( type ) invokes new Clazz( )
f.create( type, 'hello' ) invokes new Clazz( 'hello' )
f.create( type, 'hello', props ) invokes new Clazz( 'hello', props )

Factory.NONE

In this strategy, no args are passed to the Class/Function

f.create( type ) invokes new Clazz( )
f.create( type, 'hello' ) invokes new Clazz( )
f.create( type, 'hello', props ) invokes new Clazz( )

Factory.LOOKUP

When using this strategy, the Factory acts as a lookup, and Factory.create() is the same as Factory.get(). The registered object is just returned

f.create( type ) invokes Clazz
f.create( type, 'hello' ) invokes Clazz
f.create( type, 'hello', props ) invokes Clazz

Factory.MERGE

This strategy is a variant of the ARGS strategy. The type/object is merged into the first parameter.

f.create( json ) invokes new Clazz( { model : json } )
f.create( json, { value : 1 } ) invokes new Clazz( { model : json, value : 1 } )
f.create( json, { value : 1 }, props ) invokes new Clazz( { model : json, value : 1 }, props )

Factory.MERGE uses 'model' as the merge key. If you wish to make it something else, use the Factory.mergeStrategy( 'otherName' ) to create a custom merge strategy.

Custom Strategy

You can define your strategy by passing your own function in via the options. The function be invoked with:

  // factory is the invoking factory
  // clzz is the item registered against the type
  // typeOrObj is the first argument into create
  // ...args the remaining objects
  strategy( factory, clzz, typeOrObj, ...args )

Factory.reactStrategy

This is a strategy that will treat the first and second arguments passed into create() as props. The first argument will be merged into the second (the props) at a specified field name ( defaults to 'model' ). For this to work, you must supply the React object to the strategy as well:

import React from 'react'

const f = new Factory( Factory.reactStrategy( React, 'model' ) )
f.add( 'myComponent', MyComponent )

const myDataItem = { type : 'myComponent', data : 'values' }

...

<div>
  {f.create( myDataItem, { prop1 : 1, prop2 : 2 } )}
</div>

// will result in
<div>
  <MyComponent model={myDataItem} prop1={1} prop2={2}/>
</div>
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