GraphQL

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data (https://graphql.org). GraphQL is ported to two Smalltalk dialects, Pharo (6.1) and VisualWorks (7.4 & 8.3).

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Installation on Pharo

Execute the following incantation in a Playground:

Metacello new
    baseline: 'GraphQL';
    repository: 'github://OBJECTSEMANTICS/GraphQL';
    load.

GraphQL is also available in the Pharo Catalog Browser:

1. Open World Menu then Tools >> Catalog Browser
2. In search input write: Graphql
3. Load it

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Installation on VisualWorks 7.4

This project works on VisualWorks 7.4, to install GraphQL please execute the next piece of code

| dir file |
dir := Dialog requestDirectoryName: 'Choose the graphql parcels directory'.
dir isEmpty ifTrue: [^ self].
dir:= dir, (String with: Filename separator).
#('PetitExtensions' 'PetitParser' 'PetitTests'
 'GraphQLBeta' 'GraphQLExtensions' 'GraphQLBetaDemoSite') do: [:fn | 
 file := dir, fn, '.pcl'.

 file asFilename exists ifFalse: [self error: 'Missing parcel!', file asString].
 Parcel loadParcelFrom: file asFilename
  ].

Once load all the parcels of our project. If everything is going well, all the test must pass, except the tests of the classes:

• GQLTypeValidatorTest
• GQLDocumentTypeValidatorTest

Development

For the moment our application works well for request based on selection sets.

Internals

There are some classes very important on Visual Works for GraphQL:

• Query: It's the entry point by default of the demo. Also on the class side has defined the schema used by the demo.
• GraphQLBetaDemoSite: It's the class to start the demo, it works with the schema of the Query class, the entry point is a Query instance and returns the JSON results.
• GraphQL: It's the class that attends request and return the answer.

If you want to add your data to the Schema, you can modify the schema method on the class side of Query. Remember that the schema is defined as a text and follows the specifications of GraphQL. Also don't forget to create all the necessary methods (operations) on the instance side of Query to provide the answer according to the schema defined.

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Installation on VisualWorks 8.x

Execute the next code

| dir file |
dir := Dialog requestDirectoryName: 'Choose the graphql parcels directory'.
dir isEmpty ifTrue: [^ self].
dir:= dir, (Core.String with: Filename separator).
#('PetitParser' 'PetitTests' 'PetitExtentions' 'GraphQLBeta' 'GraphQLJSON' 'GraphQLBetaExtentions' 'Sport' 'Swazoo' 'GraphQLDemoSite') do: [:fn | 
 file := dir, fn, '.pcl'.

 file asFilename exists ifFalse: [self error: 'Missing parcel!', file asString].
 Parcel loadParcelFrom: file asFilename
  ].

After loading these parcels, you should be able to run (i) all the tests of GraphQL without any failure and (ii) the demos given below

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Feature ideas

This list describes a roadmap of our effort

• Complete parsing of schema.
• Complete parsing of any valid request.
• Interpretation of simple request based on selection sets.
• Add tests for interpretation of request with fragments.
• Interpretation of request with fragments.
• Add tests for interpretation of any valid request.
• Interpretation of any valid request.
• Add tests for error handling.
• Error handling.
• Add tests for type checking rules.
• Type checking of the rules.
• Add tests for introspection.
• Introspection.

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Quick Demo

Our distribution contains a small demo, which works both on Pharo and VisualWorks. Execute the following steps:

1. Open a workspace and write the following line:

GraphQLBetaDemoSite demoStart

2. Open the browser and go to the url: localhost:8888/
3. Write the following request on the text area:

{
	allFilms{
		name	
	}
}

4. Press the button Submit.
5. And you will have the response for this request.

Another Quick Demo

1. Define the class Hero:

Object subclass: #Hero
	instanceVariableNames: 'name planet'

And the following methods:

Hero>>name
	^ name

Hero>>name: aString
	name := aString
	
Hero>>planet
	^ planet
	
Hero>>planet: aString
	planet := aString

2. Define a method answering a set of heroes:

Query>>heroes
    | c |
    c := OrderedCollection new.
    c add: (Hero new name: 'Superman'; planet: 'Krypton').
    c add: (Hero new name: 'Mars pathfinder'; planet: 'Mars').
    c add: (Hero new name: 'Curiosity'; planet: 'Mars').
    c add: (Hero new name: 'Philae'; planet: 'comet 67P/Churyumov–Gerasimenko').
    ^ c

3. Write the following schema:

Query class>>schema
	^ 'type Query{
		heroes: [ Hero ]
	},
	type Hero{
		name : String
		planet : String
	}'

4. Open a workspace and write the following line:

GraphQLBetaDemoSite demoStart

5. Open the browser and go to the url: localhost:8888/
6. Submit the following request within the web browser:

{
	heroes{
		name
		planet	
	}
}

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Acknowledgement

We are very grateful to Lam Research for sponsoring part of this effort.