Angular 依赖性注入 changeDetection 可拖拽的属性型指令

4.1 依赖性注入

令牌 构建 依赖

Injector Provider Object 难。。

4.2 changeDetection

检查变化的策略：默认：全局检查,

改为onpush策略，减少全局检查的频率，大应用可以以此提高性能

(changeDetection:ChangeDetectionStrategy.OnPush)

然后在constructor中申明ChangeDetectorRef，再调用它的markDetector方法

constructor(...,private cd:ChangeDetectorRef )
xx(){
...
this.cd,markForCheck();
}

4.3 指令

指令：组件是一种带模板的指令

指令分为结构型（Structural）指令和属性型（Attribute）指令

Renderer2 和 ElementRef

Angular不提倡直接操作DOM，这是一个危险的行为

对于DOM的操作应该通过Renderer2来进行，ElementRef可以理解为指向DOM元素的引用

drag-drop 拖拽
Can't bind to 'app-draggable' since it isn't a known property of 'mat-list-item'.
1. If 'mat-list-item' is an Angular component and it has 'app-draggable' input, then verify that it is part of this module.
2. If 'mat-list-item' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.
3. To allow any property add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component. ("
'priority-emergency':item.priority===1
}"
[ERROR ->][app-draggable]="true"
[draggedClass]="drag-start"
(click)="onItemClick()"
"): ng:///TaskModule/TaskItemComponent.html@7:2
--->莫名其妙 多保存几次就好了

[app-draggable]="true"
[draggedClass]="'drag-start'"   不加''会认为是成员变量，找不到就是undefined