inject() — vue Function Reference

Source Code

src/v3/apiInject.ts lines 44–71

export function inject(
  key: InjectionKey<any> | string,
  defaultValue?: unknown,
  treatDefaultAsFactory = false
) {
  // fallback to `currentRenderingInstance` so that this can be called in
  // a functional component
  const instance = currentInstance
  if (instance) {
    // #2400
    // to support `app.use` plugins,
    // fallback to appContext's `provides` if the instance is at root
    const provides = instance.$parent && instance.$parent._provided

    if (provides && (key as string | symbol) in provides) {
      // TS doesn't allow symbol as index type
      return provides[key as string]
    } else if (arguments.length > 1) {
      return treatDefaultAsFactory && isFunction(defaultValue)
        ? defaultValue.call(instance)
        : defaultValue
    } else if (__DEV__) {
      warn(`injection "${String(key)}" not found.`)
    }
  } else if (__DEV__) {
    warn(`inject() can only be used inside setup() or functional components.`)
  }
}