Variables

We often don’t know argument values until our code is being run—for instance, we won’t always want to query for user #1. The user ID we want will depend on which profile page we’re displaying. While we could edit the document at runtime (like { user(id: ' + currentPageUserId + ') { name }}'), we recommend instead using static strings and variables. Variables are declared in the document, and their values are provided separately, like this:

query UserName($id: Int!) { 
  user(id: $id) {
    name
  }
}

{
  "id": 2
}

After the operation name, we declare ($id: Int!): the name of the variable with a $ and the type of the variable. Int is an integer and ! means that it's required ("non-null"). Then, we use the variable name $id in an argument in place of the value: user(id: $id) instead of user(id: 2). Finally, we send a JSON object with variable values along with the query document.

We can also give variables default values, for instance:

query UserName($id: Int = 1) { 
  user(id: $id) {
    name
  }
}

If $id isn’t provided, 1 will be used.