Add custom fields and methods to query results

Add a custom field to query results

You can use the result extension component to add fields to query results. These fields are computed at runtime and are type-safe.

In the following example, we add a new virtual field called fullName to the user model.

const xprisma = prisma.$extends({
  result: {
    user: {
      fullName: {
        // the dependencies
        needs: { firstName: true, lastName: true },
        compute(user) {
          // the computation logic
          return `${user.firstName} ${user.lastName}`
        },
      },
    },
  },
})

const user = await xprisma.user.findFirst()

// return the user's full name, such as "John Doe"
console.log(user.fullName)

In above example, the input user of compute is automatically typed according to the object defined in needs. firstName and lastName are of type string, because they are specified in needs. If they are not specified in needs, then they cannot be accessed.

When you call a method in an extension, use the constant name from your $extends statement, not prisma. In the above example, xprisma.user.findFirst computes the virtual field, but prisma.user.findFirst would not.

Re-use a computed field in another computed field

The following example computes a user's title and full name in a type-safe way. titleFullName is a computed field that reuses the fullName computed field.

const xprisma = prisma
  .$extends({
    result: {
      user: {
        fullName: {
          needs: { firstName: true, lastName: true },
          compute(user) {
            return `${user.firstName} ${user.lastName}`
          },
        },
      },
    },
  })
  .$extends({
    result: {
      user: {
        titleFullName: {
          needs: { title: true, fullName: true },
          compute(user) {
            return `${user.title} (${user.fullName})`
          },
        },
      },
    },
  })

Add a custom method to the result object

You can use the result component to add methods to query results. The following example adds a new method, save to the result object.

const xprisma = prisma.$extends({
  result: {
    user: {
      save: {
        needs: { id: true },
        compute(user) {
          return () =>
            prisma.user.update({ where: { id: user.id }, data: user })
        },
      },
    },
  },
})

const user = await xprisma.user.findUniqueOrThrow({ where: { id: someId } })
user.email = 'mynewmail@mailservice.com'
await user.save()

When you call a method in an extension, use the constant name from your $extendsstatement, not prisma. In the above example, xprisma.user.findUniqueOrThrow works, but prisma.user.findUniqueOrThrow does not.