项目初始化

src/app/core/core.module.ts

@@ -0,0 +1,12 @@
+import { NgModule, Optional, SkipSelf } from '@angular/core';
+
+import { throwIfAlreadyLoaded } from './module-import-guard';
+
+@NgModule({
+  providers: []
+})
+export class CoreModule {
+  constructor(@Optional() @SkipSelf() parentModule: CoreModule) {
+    throwIfAlreadyLoaded(parentModule, 'CoreModule');
+  }
+}