Android Question [Solved] Difference in ClassModule between getMyValue and Myvalue?

Pflichtfeld · Apr 29, 2020

Is there a difference between these two sub-declarations in a Class?

B4X:

public Sub getMyvalue As Object
        Return myObject
End Sub
public Sub Myvalue As Object
        Return myObject
End Sub

Both are accessed by

B4X:

xyz=MyCls.Myvalue

or is this wrong?

Star-Dust · Apr 29, 2020

Pflichtfeld said:
Is there a difference between these two sub-declarations in a Class?

B4X:

public Sub getMyvalue As Object Return myObject End Sub public Sub Myvalue As Object Return myObject End Sub

Both are accessed by

B4X:

xyz=MyCls.Myvalue

or is this wrong?

They are both correct. but by prefixing get and set you can manage the sub as if it were a variable

B4X:

public Sub getMyvalue As Object
        Return myObject
End Sub
public Sub setMyvalue (Ob As Object)
        myObject=Ob
End Sub

B4X:

xyz=MyCls.Myvalue
MyCls.Myvalue=xyz

Pflichtfeld · Apr 29, 2020

Star-Dust said:
They are both correct. but by prefixing get and set you can manage the sub as if it were a variable

I know the different behaviour for SET. But for getting the value in both cases it is treated like a variable, isn't it?

Star-Dust · Apr 29, 2020

Above all, it is useful when you need to publish a value that is not an internal variable of the Class but of an object of the class.
Here is an example:

B4X:

public Sub getMyvalue As Object
        Return myObject.Value
End Sub
public Sub setMyvalue (Ob As Object)
        myObject.Value=Ob
End Sub

It will not be necessary to make the myObject public only to access a property of it

Star-Dust · Apr 29, 2020

Pflichtfeld said:
I know the different behaviour for SET. But for getting the value in both cases it is treated like a variable, isn't it?

YES

Sandman · Apr 29, 2020

Just a small note. If I remember correctly, it's important that the "get" and "set" don't have any CAPS in them.

So this...

B4X:

public Sub SetMyvalue (Ob As Object)
       myObject=Ob
End Sub

...should be...

B4X:

public Sub setMyvalue (Ob As Object)
        myObject=Ob
End Sub

klaus · Apr 29, 2020

This is a variable:

B4X:

Public Rotation As Double

to read or change it:

B4X:

MyClass.Rotation = 20.5
MyRotation = MyClass.Rotation

it is only an internal variable accessible from outsides.

This is a property:
get and set must be lower case.

B4X:

'gets or sets the Rotation property of the Chart
'rotates the entire chart
'Rotation in degrees
Public Sub getRotation As Double
    Return Graph.Rotation
End Sub

Public Sub setRotation (Rotation As Double)
    Graph.Rotation = Rotation
    xBase.Rotation = Graph.Rotation
End Sub

to read or change it:

B4X:

MyClass.Rotation = 20.5
MyRotation = MyClass.Rotation

The access code is the same as for the variable, but in the class it's different.
The comments before the Sub declaration are displayed in the inline help in the IDE.

This is a method:

B4X:

Public Sub SetMargins(Left As Int, Right As Int)
    LeftMargin = Left
    RightMargin = Right
End Sub

To use it:

B4X:

MyClass.SetMargins(20, 30)

You can set the values but not read them.
You can, of course, also add comments.

Pflichtfeld · Apr 29, 2020

klaus said:
to read or change it:

B4X:

MyRotation = MyClass.Rotation

it is only an internal variable accessible from outsides.
to read or change it:

B4X:

MyRotation = MyClass.Rotation

The access code is the same as for the variable, but in the class it's different.
The comments before the Sub declaration are displayed in the inline help in the IDE.

Thank you, that clears my question.

LucaMs · Apr 29, 2020

A couple of notes.

1 - Using a Property instead of a variable declared as public in the Process_Globals, has some advantages:

1a - in the two routines that usually make up a Property, you can obviously write code and therefore check that the value set is valid;

1b - while you cannot prevent the value of a public variable from being changed, you can do it with a Property, creating only the setting routine (setXXX but not getXXX);

2 - another important difference between a normal public routine and a Property (its "set part") is that only the first one can receive more than one parameter.

3 - I forgot the others I wanted to write, "listening" to the TV news ?

Pflichtfeld · Apr 29, 2020

LucaMs said:
2 - another important difference between a normal public routine and a Property (its "set part") is that only the first one can receive more than one parameter.

Ok, thank you for that! (But it applies to the set-routine. My question was about the get.)

Android Question [Solved] Difference in ClassModule between getMyValue and Myvalue?

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