Provides a value that can be injected by descendant components.
Type
function provide<T>(key: InjectionKey<T> | string, value: T): voidDetails
provide() takes two arguments: the key, which can be a string or a symbol, and the value to be injected.
When using TypeScript, the key can be a symbol casted as InjectionKey - a Vue provided utility type that extends Symbol, which can be used to sync the value type between provide() and inject().
Similar to lifecycle hook registration APIs, provide() must be called synchronously during a component's setup() phase.
Example
<script setup>\nimport { ref, provide } from 'vue'\nimport { fooSymbol } from './injectionSymbols'\n\n// provide static value\nprovide('foo', 'bar')\n\n// provide reactive value\nconst count = ref(0)\nprovide('count', count)\n\n// provide with Symbol keys\nprovide(fooSymbol, count)\n</script>See also
Injects a value provided by an ancestor component or the application (via app.provide()).
Type
// without default value\nfunction inject<T>(key: InjectionKey<T> | string): T | undefined\n\n// with default value\nfunction inject<T>(key: InjectionKey<T> | string, defaultValue: T): T\n\n// with factory\nfunction inject<T>(\n key: InjectionKey<T> | string,\n defaultValue: () => T,\n treatDefaultAsFactory: true\n): TDetails
The first argument is the injection key. Vue will walk up the parent chain to locate a provided value with a matching key. If multiple components in the parent chain provides the same key, the one closest to the injecting component will "shadow" those higher up the chain. If no value with matching key was found, inject() returns undefined unless a default value is provided.
The second argument is optional and is the default value to be used when no matching value was found.
The second argument can also be a factory function that returns values that are expensive to create. In this case, true must be passed as the third argument to indicate that the function should be used as a factory instead of the value itself.
Similar to lifecycle hook registration APIs, inject() must be called synchronously during a component's setup() phase.
When using TypeScript, the key can be of type of InjectionKey - a Vue-provided utility type that extends Symbol, which can be used to sync the value type between provide() and inject().
Example
Assuming a parent component has provided values as shown in the previous provide() example:
<script setup>\nimport { inject } from 'vue'\nimport { fooSymbol } from './injectionSymbols'\n\n// inject static value without default\nconst foo = inject('foo')\n\n// inject reactive value\nconst count = inject('count')\n\n// inject with Symbol keys\nconst foo2 = inject(fooSymbol)\n\n// inject with default value\nconst bar = inject('foo', 'default value')\n\n// inject with function default value\nconst fn = inject('function', () => {})\n\n// inject with default value factory\nconst baz = inject('factory', () => new ExpensiveObject(), true)\n</script>See also