Database context values

It is very common that we'll have some common values that we'll use in our database.

Such values might be:

• user id
• workspace id
• user role

Those values can be declared when creating clientdb and will be available in many places across clientdb.

Example use cases:

• userId field on todo entity that will default to current user id
• todo.isOwnedByCurrentUser field that will be true if todo is owned by current user

Let's write some code.

import { createDbContext, createClientDb } from "@clientdb/core";

const userIdContext = createDbContext<string>();

const db = createClientDb([todoEntitiy, listEntity], {
  contexts: [userIdContext("user-a")],
});

Our db now has userIdContext value of user-a.

Let's now extend our todoEntity to have isOwnedByCurrentUser field:

interface Todo {
  id: string;
  title: string;
  doneAt: Date;
  userId: string;
}

const todoEntity = defineEntity<Todo>({
  name: "todo",
  fields: ["id", "title", "doneAt", "userId"],
}).addView((todo, { db }) => {
  return {
    get isOwnedByCurrentUser() {
      return todo.userId === db.getContextValue(userIdContext);
    },
    // ...
  };
});

Now we can use isOwnedByCurrentUser field in every todo in our database

const todo = db.entity(todoEntity).create({
  title: "Learn clientdb",
  userId: "user-a",
});

todo.isOwnedByCurrentUser; // true

const anotherTodo = db.entity(todoEntity).create({
  title: "Learn clientdb",
  userId: "user-b",
});

todo.isOwnedByCurrentUser; // false

Using context values as default values

We can also read context values as default values for our fields.

const todoEntity = defineEntity<Todo>({
  name: "todo",
  fields: ["id", "title", "doneAt", "listId", "userId"],
  getDefaultValues(db) {
    return {
      userId: db.getContextValue(userIdContext),
    };
  },
}).addView((todo, { db }) => {
  // ...
});

Now, if we created todo without passing userId - it will default to current user id.

const todo = db.entity(todoEntity).create({
  title: "Learn clientdb",
});

todo.userId; // "user-a"
todo.isownedByCurrentUser; // true

Note: Context values are constant and has to be defined at the time of creating clientdb. If you'd like to modify context values, you'd have to create a new clientdb. We're planning to support mutable context values in the future.