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Is this a bug in the View Parent Code button?

  • Article

We received a bug report

Steps to Reproduce :

1) Create MyButtonClass1 class of MyButtonLibrary1. Add code to click method.

2) Create MyFormClass1 class of MyFormLibrary1.

3) Add commandbutton of class created in step1. Add code to commandbutton's click method.

4) Create MyFormClass2 class of MyFormLibrary2. Add code to commandbutton's click method. Include DODEFAULT()

5) Create MyFormClass3 class of MyFormLibrary3. Press "View Parent Code" button in editor while viewing commandbutton click method.

Actual Results :

When the "View Parent Code" button is clicked in step 5 the parent class hierarchy shown does not include the subclass created in step 3. This is the faulty behavior.

However, when an object is created form class MyFormClass3 and the commandbutton clicked, the method is in fact executed. This is correct behavior.

Expected Results :

I would expect that "View Parent Code" would show all parent classes that in fact are executed as DODEFAULT() is issued.

While this is not a "show stopper" it is a clear and important error.

After some wrangling, manipulation and guessing, I managed to create code to reproduce the issue (below)

When the designer comes up, there are 2 entries in the View Parent Code

MYFORMCLASS2 (which shows “Step 4” in the code)

MYBUTTONCLASS1 (which shows “Baseclass” in the code)

When you click the button, this is output to the screen:

MYFORMCLASS3.CMD.CLICK Step 5

MYFORMCLASS2.CMD.CLICK Step 4

MYFORMCLASS1.CMD.CLICK Step 3

MYBUTTONCLASS1.CLICK Button Baseclass_

Is this a bug? If so, how many items do you expect to see when the View Parent Code button is clicked? What exactly should each of them say? What if there were more levels of inheritance?

CLEAR

CLEAR ALL

ERASE MyButtonLibrary*.*

ERASE MyFormLibrary*.*

*1

Create CLASS MyButtonClass1 of MyButtonLibrary1 as commandbutton nowait

ASELOBJ(aa,1)

ox=aa[1]

ox.writemethod("click",GenCode("Button Baseclass"))

KEYBOARD 'y' && send a "Y" to "Do you want to save changes" dialog

RELEASE WINDOWS "Class Designer" && close the designer

DOEVENTS

*2

Create CLASS MyFormClass1 of MyFormLibrary1 as form nowait

ASELOBJ(aa,1)

ox=aa[1]

ox.AllowOutput=.f. && so output goes to screen

ox.left=300 && so form is not on top of output

*3

ox.Newobject("cmd","MyButtonClass1","MyButtonLibrary1")

ox.cmd.writemethod("click",GenCode("Step 3"))

ox.cmd.caption="Click me"

KEYBOARD 'y' && send a "Y" to "Do you want to save changes" dialog

RELEASE WINDOWS "Class Designer" && close the designer

DOEVENTS

*4

Create class MyFormClass2 of MyFormLibrary2 as MyFormClass1 from MyFormLibrary1 NOWAIT

ASELOBJ(aa,1)

ox=aa[1]

ox.cmd.writemethod("click",GenCode("Step 4"))

KEYBOARD 'y' && send a "Y" to "Do you want to save changes" dialog

RELEASE WINDOWS "Class Designer" && close the designer

DOEVENTS

*5)

Create class MyFormClass3 of MyFormLibrary3 as MyFormClass2 from MyFormLibrary2 nowait

ASELOBJ(aa,1)

ox=aa[1]

ox.cmd.writemethod("click",GenCode("Step 5. Examine 'View Parent Code' button"))

KEYBOARD 'y' && send a "Y" to "Do you want to save changes" dialog

RELEASE WINDOWS "Class Designer" && close the designer

DOEVENTS

KEYBOARD '{ALT+i}'

MODIFY CLASS MyFormClass3 of MyFormLibrary3 METHOD cmd.click

ox=NEWOBJECT("MyFormClass3","MyFormLibrary3")

ox.show(1)

PROCEDURE gencode(str as String)

      TEXT TO mycode NOSHOW TEXTMERGE

      ?PROGRAM(),"<<str>>"

      DODEFAULT()

      ENDTEXT

      RETURN mycode

Comments

  • Anonymous
    November 15, 2005
    Not a bug.

    In all cases the button class MyButtonClass1 is that class.

    However, when you drop a class on a form class you are creating an "instance" not a class.

    So, when you subclass the form the code in the click method of the button instance isn't in the parent button class.

    The best practice would be to have to button class click method call a method on the form. Then, your form subclass can override that method. This gives you a cleaner UI and allows you to reuse the button class rather than putting code in the buttons instance.
  • Anonymous
    November 15, 2005
    It is a bug.

    It is not easy to fix it.

    However, if you fix it, can you also fix the similar issue for a columns defined inside a Prg.

    Repro:
    1. It creates a class column in a Prg, with some method.
    2. Add it as memberClass into a grid.

    result:
    In Class Designer "View Parent Tails" for the grid columns are empty.

    Thanks.
  • Anonymous
    November 16, 2005
    Sounds to me it is a bug in the purist sense as Bob Archer pointed out that the missing method code belongs to an instance of the class not the class itself.

    However it may be a good idea to show all the methods in the call chain when "viewing parent code" to make it consistent with FoxPro tendency to blur the difference between instance programming and subclassing.
  • Anonymous
    December 05, 2005
    Hi Calvin,

    I ran into this problem because I purchased a framework which has a compund object (form plus dataaccess object). I then created an intermediate subclass to which I added objects and code meant to be be shared by several apps. Then I create an app specific subclass from that and from that I create my forms.

    Whether it is good design or not (and it may not be), I think is a bug because the design time behavior does not predict what will actually ocurr at runtime.

    Thank you for your attention,

    Alex