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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‚Äč

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.