Detailed explanation of CocosCreator message distribution mechanism

/**
 * Message monitoring callback method */
export type NotifyListener = (src: any, data: any) => void;

private static msg2listDict: Dictionary< string, Array<NotifyListenerInfo> > = new Dictionary< string, Array<NotifyListenerInfo> >();

/**
 * Add multiple listeners, need to remove manually * @param msg
 * @param listener
 * @param target
 */
public static addListener(msg: string, listener: NotifyListener, target?: any): void {}
 
/**
 * Add a one-time listener and remove it after the event is triggered* @param msg
 * @param listener
 * @param target
 */
public static addOnceListener(msg: string, listener: NotifyListener, target?: any): void {}
 
/**
 * Remove the listener specified by the specified message * @param msg
 * @param listener
 */
public static removeMsgListener(msg: string, listener: NotifyListener): void {}
 
/**
 * Remove all listeners of the specified message * @param msg
 */
public static removeMsgAllListeners(msg: string): void {}
 
/**
 * Remove the specified target's monitoring of the specified message * @param msg
 * @param target
 */
public static removeTargetMsgListen(msg: string, target: any): void {}
 
/**
 * Remove all message listeners of the specified target * @param target
 */
public static removeTargetAllMsgListen(target: any): void {}
 
/**
 * Send message * @param msg
 * @param src
 * @param data
 */
public static notify(msg: string, src: any, data: any): void {}

private static listener2add: Array<NotifyListenerInfo> = [];

// The message is being dispatched and put into the queue to be added if (NotifyCenter.notifyMsgs.indexOf(msg) >= 0) {
    NotifyCenter.listener2add.push(info);
    return;
}

private static listener2remove: Array<NotifyListenerInfo> = [];

// The message is being dispatched and put into the queue to be removed if (NotifyCenter.notifyMsgs.indexOf(msg) >= 0) {
    NotifyCenter.listener2remove.push(list[i]);
} else {
    list.splice(i, 1);
}

// The queue does not exist, no need to process let list = NotifyCenter.msg2listDict.get(msg);
if (!list) {
    return;
}
 
// Mark the message as being dispatched. Multiple messages may be dispatched at the same time. The same message may be marked multiple times. NotifyCenter.notifyMsgs.push(msg);
 
// Process message dispatch for (let i = 0, n = list.length; i < n; i++) {
    NotifyCenter._dispatch(list[i], src, data, false);
}

// In the removal queue, no dispatch if (NotifyCenter.listener2remove.indexOf(info) >= 0) {
    return;
}

// Process the queue to be added for (let i = 0, n = msg2add.length; i < n; i++) {
    if (listener2add[i].msg == msg) {
        NotifyCenter._dispatch(listener2add[i], src, data, true);
    }
}