zoukankan      html  css  js  c++  java
  • AX7: Accessing privateprotected class methods and members from extension code

    All class member variables are protected by default in AX 7, so it is impossible to access them from extensions. It becomes a real problem when you try to extend classes like SalesLineType.

    For example, we want to add custom logic on sales line insert event. Call to super() is commented out so we cannot create pre or post event handlers. We may try to create event handlers for SalesLineType.insert() mehtod, but we won’t get access to salesLine buffer because this variable is protected.

    There are two options: use overlaying or use reflection.

    Overlaying is preferable approach, but today we will talk about reflection to explain this option.

    Reflection is usually used for unit testing in case you need to cover protected or private code and it is hard to call this code using public API.

    It has bunch of disadvantages:

    It breaches entire basis of OO programming. Slow performance. Possible issues with future updates. Private methods could be changed at any time. However, once you may get into situation where it could be еру only option so it’s better to know about this possibility.

    Let’s try to change some fields on sales line insert using reflection.

    Create new event handler class for SalesLineType and subscribe to post insert:

    using System.Reflection;
     
    /// <summary>
    /// Handles events raised by <c>SalesLineTypeEventHandler</c> class.
    /// </summary>
    public class SalesLineTypeEventHandler
    {
        [PostHandlerFor(classStr(SalesLineType), methodStr(SalesLineType, insert))]
        public static void SalesLineType_Post_insert(XppPrePostArgs _args)
        {
            SalesLineType salesLineType = _args.getThis();
     
            var bindFlags = BindingFlags::Instance | BindingFlags::NonPublic;
     
            var field = salesLineType.GetType().GetField("salesLine", bindFlags);
     
            SalesLine salesLine = field.GetValue(salesLineType);
     
            if (salesLine)
            {
                salesLine.MyNewField = 42;
                salesLine.doUpdate();
            }
        }
    }

    Also we can call private or protected method:

    var bindFlags = BindingFlags::Instance | BindingFlags::NonPublic;
     
    var methodInfo = salesLineType.GetType().GetMethod(methodStr(SalesLineType, checkQuantityUpdate), bindFlags);
     
    if (methodInfo)
    {
        methodInfo.Invoke(salesLineType,  new System.Object[0]());
    }

    You can read more about reflection on msdn

  • 相关阅读:
    二分查找小结
    FZU みねちゃんの修罗场(从一堆出现三次的数中找出出现两次的数)
    《C陷阱与缺陷》杂记
    HDU 1846 Brave Game(巴什博弈)
    【转载】并查集详解
    第七次作业——学末总结
    STL之vector
    fzuoop期中练习
    MFC 文件对话框
    第六次作业——利用MFC实现计算器图形界面以及简单四则运算表达式批处理
  • 原文地址:https://www.cnblogs.com/dingkui/p/6266049.html
Copyright © 2011-2022 走看看