So the window has not been shown by this point.
Or it has been closed rather than hidden.
try turning the
ActionAntagonistQuestions
variable into a computed property
In the GET method, do this:
if mActionAntagonistQuestions = nil then
mActionAntagonistQuestions = new WinAntagonistActionAntagonistQuestions
end if
return mActionAntagonistQuestions
No, this is not the Main Window. Next to the WinMain there are 12 separate windows and at this moment I am getting this same NilObjectException on every window.
Xojo tells me that it cannot assign a value to this property:
Module1.mActionAntagonistQuestions.Get, line 2
Cannot assign a value to this property
mActionAntagonistQuestions = new WinAntagonistActionAntagonistQuestions
You need to have a property to store the actual value, thatâs what the m property is for. In a few style guides, the m prefix commonly means âprivateâ.
To super simplify and illustrate, youâll end up with something similar to this:
When you access ComputedProperty the Get function runs, and because the actual value is nil a new instance is created before the actual value mComputedProperty is returned.
Update: You can also get Xojo to do a lot of the legwork for you on any existing property by using the contextual menu.
You should have a computed property named ActionAntagonistQuestions but your screenshot shows that the computed property is named mActionAntagonistQuestions.
You can right-click ActionAntagonistQuestions and select âconvert to computed propertyâ
that way you end with your computed property (with some code in Get and Set) and the corresponding private âmâ property (mActionAntagonistQuestions)
You will just need to adjust the Get code.
Edit: I think Tim edited his post while I was taking the screenshots. So this information is the same as above.
Edit2:
The Opening event of those windows does not execute just by opening your project.
As others have pointed out, you didnt
but instead created a new variable yourself, with the m
Delete your mActionAntagonistQuestions
and convert ActionAntagonistQuestions
Thanks, I fixed this. I wasnât sure yet what a Computed Property was, but now I understand what it is doing.
Thanks for the explanation, Tim, I was a little confused what the Computed Property was about but now itâs clear to me.
André,
when you reach case(s) like this, create a brand new project, and try to make it work (using smal named properties, windows names, etc.).
The simple fact of doing this, will allow you to resolve the trouble, fast. Once done, you only have to set the solution in the main project.
Same with new feature: implement it in a brand new project, once it works, you only have to add it into the main project.
This will takes a bit of time (probably less than waiting a good answer from here) and allow yopu to keep h-you hair in your head / your computer on your desktop (instead of sending it through the window) ;).
Now, you use the was to develop you prefer.
You create useful and meaningful names (for you), but how can people can help when they have to read code with so long names:
Var antagonistIsSmart As String =
ActionAntagonistQuestions.CCAntagonistQuestionList3Applied.Text_AntagonistIsSmart.text
//Here I created a variable to make the long path shorter.
Also, following advices is a good idea. For example:
Var sql As String
sql = "UPDATE Customer SET City='" + CityField.Text + "' WHERE PostalCode='" + PostalCodeField.Text + "'"
Try
db.ExecuteSQL(sql)
This code comes from the Xojo documentation, ExecuteSQL
This allows you to use the sql string to be reported in System.DebugLog sql
You will be able to read the sql contents once you click in this icon (in the IDE):
This icon is located at the ideâs bottom right (bottom-center of the screen).
Thanks for the advice, Emile. I was still not able to fix this problem, but I am going to let it rest for some weeks and work on other parts of the program. Maybe when I come back to it I have some fresh eyes and see what it going on.
Is your window set to ImplicitInstance? If so, you wouldnât have to use that separate property and can rely on it being not nil without further initialization.
I am using DesktopWindows and they donât have the Implicit Instance property.
Sure they have. Itâs just the property was placed on the second tab now. And is not in the docs property overview.
aah, I didnât know that. I read somewhere that this wasnât very trustable to use and that it was taken out because of that. It was already enabled for all the windows.
If so, try to use the window directly instead of creating a new one. Implicit instance is reliable but can be tricky at times â especially when you find you need that window more than once.
In your case, I donât see that limitation. You shouldnât run into NOEs with it.
And now it works! Thanks.
Actually, after having entered all the code, now when I open a window with the button press, there is a new window opened for every text field on that window. And when I enter text in text field on that window, a new window is opened as well. I believe that this is one of the problems when using Implicit instance.
No, thats what happens if you use the NEW keyword on the window type.
if you have a window called frmBanana
And you say frmBanana.show, then the ONE AND ONLY banana window will appear.
But if your button contains code that says
Var myBanana as new frmBanana
myBanana.show
Then you will get multiple copies of the window.
Each method has itâs benefits and problems.
If you want one and only copy, always talk about frmBanana, and never do a new as
Ofcourse, I understand the banana problem, however in this case, clicking in a text field should not create a New Window, or in my case, 12 new windows (there are 12 text fields on this specific window. No âAs Newâ used anywhere here.
update:
Ok, I understand now that a window with Implicit instance enabled is in fact always open although hidden, and when an object on a hidden window is being activated, that window will show. Good to know. I should in that case start to work with hide and show windows
Yes, absolutely. You can consider a window you design in the IDE being a custom window subclass. So whenever multiple windows of that same type are necessary, you can create a new instance with the New command. In that case it is often better to loop through the existing windows if you want to retrieve it instead of having a separate property for it.
The same is valid for a window with ImplicitInstance set to True, but additionally one instance of that window class will be created, having the same name as the class. This can lead to confusions, especially at is indeed better to hide the window instead of closing it. But in any case you encounter several instances of the same window there must be a new somewhere in your code or something similar leading to an instantiation.