Middleware

You can use middleware to affect the evaluation of fields in your schema.

A middleware is any object that responds to resolve(*args, next_middleware).

Inside that method, it should either:

  • Send resolve to the next middleware to continue the evaluation; or
  • Return a value to end the evaluation early.

Resolve arguments

Middlewares resolve is invoked with several arguments:

  • next represents the execution chain. Call next to continue evalution.
  • root is the root value object passed throughout the query.
  • info is the resolver info.
  • args is the hash of arguments passed to the field.

Example

This middleware only continues evaluation if the field_name is not 'user'

class AuthorizationMiddleware(object):
    def resolve(self, next, root, info, **args):
        if info.field_name == 'user':
            return None
        return next(root, info, **args)

And then execute it with:

result = schema.execute('THE QUERY', middleware=[AuthorizationMiddleware()])