Page Link fields are added to the WPGraphQL Schema as a field with a Union of Possible Types the field is configured to allow.
Since Page Link fields can be configured to be limited to certain Post Types, the Union will represent those Types.
For example, if the Post Object field is configured to allow Posts of the post and page types to be selected:
Then the Union type for the field will allow Post and Page types to be returned, as seen in the Schema via GraphiQL:
Here, we have a Page Link field named page_link on the Post Edit screen within the "ACF Docs" Field Group, and the value is set to the "Sample Page" page.
This field can be Queried in GraphQL like so:
{
post(id: "acf-example-test", idType: URI) {
acfDocs {
pageLink {
__typename
... on Post {
id
title
date
}
... on Page {
id
title
}
}
}
}
}and the results of the query would be:
{
"data": {
"post": {
"acfDocs": {
"pageLink": {
"__typename": "Page",
"id": "cGFnZToy",
"title": "Sample Page"
}
}
}
}
}Here, we set the value to the "Hello World" Post:
And the results of the same query are now:
{
"data": {
"post": {
"acfDocs": {
"pageLink": {
"__typename": "Post",
"id": "cG9zdDox",
"title": "Hello world!",
"date": "2020-02-20T23:12:21"
}
}
}
}
}