什么是ngrx createSelector和createFeautureSelector？

Question

我一直在阅读ngrx示例应用程序的代码并找到两个函数调用

1. createFeatureSelector<AuthState>('auth');

和

2. createSelector(selectAuthState,(state: AuthState) => state.status);

这是做什么的？

export const selectAuthState = createFeatureSelector<AuthState>('auth');

export const selectAuthStatusState = createSelector(
  selectAuthState,
  (state: AuthState) => state.status
);

Answer 1

它用作存储切片选择的优化步骤.例如,如果你为某些商店切片返回一些繁重的计算结果,那么使用 createSelector将执行memoization,这意味着它将跟踪选择器的最后输入参数,如果它们与当前的相同,它将立即返回最后的结果而不是重复计算.

ref:https://github.com/ngrx/platform/blob/master/docs/store/selectors.md