this._tick里調用this.changeDetectorRef.detectChanges():

首先從RootViewRef開始檢測：

context里能看到Component的數據：

renderComponentOrTemplate:

refreshView里會調用init和check hook:

/*** Executes post-order init and check hooks (one of AfterContentInit, AfterContentChecked,* AfterViewInit, AfterViewChecked) given a view where there are pending init hooks to be executed.* @param lView The LView where hooks are defined* @param hooks Hooks to be run* @param initPhase A phase for which hooks should be run* @param nodeIndex 3 cases depending on the value:* - undefined: all hooks from the array should be executed (post-order case)* - null: execute hooks only from the saved index until the end of the array (pre-order case, when* flushing the remaining hooks)* - number: execute hooks only from the saved index until that node index exclusive (pre-order* case, when executing select(number))*/ function executeInitAndCheckHooks(lView, hooks, initPhase, nodeIndex) {ngDevMode &&assertNotEqual(initPhase, 3 /* InitPhaseCompleted */, 'Init pre-order hooks should not be called more than once');if ((lView[FLAGS] & 3 /* InitPhaseStateMask */) === initPhase) {callHooks(lView, hooks, initPhase, nodeIndex);} }

使用Directive實例調用hook：

function rememberChangeHistoryAndInvokeOnChangesHook() {const simpleChangesStore = getSimpleChangesStore(this);const current = simpleChangesStore === null || simpleChangesStore === void 0 ? void 0 : simpleChangesStore.current;if (current) {const previous = simpleChangesStore.previous;if (previous === EMPTY_OBJ) {simpleChangesStore.previous = current;}else {// New changes are copied to the previous store, so that we don't lose history for inputs// which were not changed this timefor (let key in current) {previous[key] = current[key];}}simpleChangesStore.current = null;this.ngOnChanges(current);} }

ngOnChanged hook被調用的前提是，從getSimpleChangesStore返回的simpleChangesStore里的current字段不為空：

更多Jerry的原創文章，盡在：“汪子熙”:

總結

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