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GraphQL Implementation

The use of the package starts with creating a root object. Next the root is used to load a GraphQL schema file which must be in SDL format. Instances of schema types are created to capture the schema information as the SDL file is parsed. A second pass is made over the object to setup references or pointers to the correct types. The first parsing pass generates place holders if the referenced GraphQL type has not been loaded yet. Finally validation is performed. Validation includes GraphQL validation as well as a check of any go types referenced by directives in the schema file.

Requests can be either SDL or JSON. Both are parsed into document types that validated against the schema. After a successful validation the resolve processing is started.

There are three alternatives for resolving a document into a JSON result. One uses a single resolver function. Another uses a Resolver interface and the third mkes use of reflection to marshal the request data into function calls on specific go types. In each case the results of the resolving are used to for a tree that is then converted to JSON.

graph LR

Schema --> Evaluator
Request --> Evaluator
Evaluator --> native-go-value
native-go-value --> JSON
Loading

Schema Types

The schema types includes the types that represent the GraphQL schema including GraphQL types, scalars, enums, directives, and others that are defined in a SDL document. These types are parsed from an SDL file and can be used to generate an SDL.

Query, Mutation, and Subscriptions Types

The Query, Mutation, and Subscriptions are the requests that can be made to the package and are referred to as documents or document types. The doc types are evaluated to for responses to requests whether those responses be immediate or for subscriptions deferred until events occur. These types include fragments, queries, mutations, and others.

Values

The result of resolving a document are referred to as the values. The value types all map to a JSON type. Any scalar that does not map directly is mapped as a string. The Time scalar is an example of that. The scalar types all implement functions that coerce input as well as function output values into an internal type. The JSON() function of each will generate the appropriate value suitable for conversion to response JSON.

The value types as golang types are:

  • map[string]interface{}
  • []interface{}
  • float64
  • int64
  • string
  • boolean
  • nil