Android Question Get variable value by string of name

hung · Dec 30, 2023

Here is what I want

B4X:

Sub Process_Globals
    Private gs_appver As String = "2312xx"
    Private gs_appname As String = "App name"
End sub

Sub Showall()
    ToastMessageShow(varval("gs_appver"), True)
    ToastMessageShow(varval("gs_appname"), True)
End sub

Is there a function in B4x similar as "varval()"?

LucaMs · Dec 30, 2023

ToastMessageShow(gs_appver, True)

[ - 6 ]

ilan · Dec 30, 2023

LucaMs said:

aeric · Dec 30, 2023

Of course such function doesn't exist in B4A or else you can already use it.

With B4XPages, I can create the function.

Note: Only valid for String variables.

B4X:

Sub Class_Globals
    Private Root As B4XView
    'Private xui As XUI
    Private varmaps As Map
    Private gs_appver As String = "2312xx"       'ignore
    Private gs_appname As String = "App name"    'ignore
End Sub

Public Sub Initialize
'    B4XPages.GetManager.LogEvents = True
    varmaps.Initialize
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    Root.LoadLayout("MainPage")
    GenerateVarMaps
End Sub

Sub ShowAll
    ToastMessageShow(varval("gs_appver"), True)
    ToastMessageShow(varval("gs_appname"), True)
End Sub

Private Sub varval (key As String) As String
    Return varmaps.Get(key)
End Sub

Private Sub GenerateVarMaps
    Dim strMe As String = Me
    Dim Fields() As String = Regex.Split2(",", Regex.MULTILINE, strMe.SubString2(1, strMe.Length-1))
    
    For Each Field As String In Fields
        Dim ExcludeList As List = Array("b4xcollections", "b4xpages", "main", "root", "starter", "xui")
        If Field.Contains("=") Then
            Dim KeyValue() As String = Regex.Split("=", Field)
            KeyValue(0) = KeyValue(0).Trim
            KeyValue(1) = KeyValue(1).Trim
            If ExcludeList.IndexOf(KeyValue(0)) < 0 Then
                varmaps.Put(KeyValue(0), KeyValue(1))
            End If
        End If
    Next
End Sub

Private Sub Button1_Click
    ShowAll
End Sub

aeric · Dec 30, 2023

From below similar threads,
This one may work for Int variables and Default template.

Help! Getting and using the name of a variable/array?

Hi guys! This might be hard to explain, but I'll do my best. Consider the following pseudo-code: Dim a, b, c, d, e, f, g, ... As Int GetUserInput("Which variable? ", VarName) SetVar(VarName, 10) 'Output: '(c = 0) 'Which variable? c '(c = 10) How can I do this without having to do this with...

www.b4x.com

ilan · Dec 30, 2023

aeric said:

Of course such function doesn't exist in B4A or else you can already use it.

With B4XPages, I can create the function.

Note: Only valid for String variables.

B4X:

Sub Class_Globals
    Private Root As B4XView
    'Private xui As XUI
    Private varmaps As Map
    Private gs_appver As String = "2312xx"       'ignore
    Private gs_appname As String = "App name"    'ignore
End Sub

Public Sub Initialize
'    B4XPages.GetManager.LogEvents = True
    varmaps.Initialize
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    Root.LoadLayout("MainPage")
    GenerateVarMaps
End Sub

Sub ShowAll
    ToastMessageShow(varval("gs_appver"), True)
    ToastMessageShow(varval("gs_appname"), True)
End Sub

Private Sub varval (key As String) As String
    Return varmaps.Get(key)
End Sub

Private Sub GenerateVarMaps
    Dim strMe As String = Me
    Dim Fields() As String = Regex.Split2(",", Regex.MULTILINE, strMe.SubString2(1, strMe.Length-1))
   
    For Each Field As String In Fields
        Dim ExcludeList As List = Array("b4xcollections", "b4xpages", "main", "root", "starter", "xui")
        If Field.Contains("=") Then
            Dim KeyValue() As String = Regex.Split("=", Field)
            KeyValue(0) = KeyValue(0).Trim
            KeyValue(1) = KeyValue(1).Trim
            If ExcludeList.IndexOf(KeyValue(0)) < 0 Then
                varmaps.Put(KeyValue(0), KeyValue(1))
            End If
        End If
    Next
End Sub

Private Sub Button1_Click
    ShowAll
End Sub

But why?
Why not just work with variables?

emexes · Dec 30, 2023

aeric said:
With B4XPages, I can create the function.

Does that function only work under B4A or B4XPages? I tried with B4J no UI but the only string I get out of Me is "class.b4j.example.main".

aeric · Dec 30, 2023

ilan said:
But why?
Why not just work with variables?

I have no idea.
I just follow what was requested.
Perhaps he has hundreds of variables and he wants to get the value of the variable by combining 2 or more strings or working with a loop.
eg. "gs_" & "app" & "ver"

aeric · Dec 30, 2023

emexes said:
Does that function only work under B4A or B4XPages? I tried with B4J no UI but the only string I get out of Me is "class.b4j.example.main".

As I mentioned.
Only works with B4XPages (B4A and B4J).

aeric · Dec 30, 2023

If you want to work with B4X or non-UI just manually add all variables into a Map. ?

B4X:

Sub Process_Globals
    Private varmaps As Map
    Private gs_appver As String = "2312xx"
    Private gs_appname As String = "App name"
    Private gs_appbuild As Float = 2.5
End Sub

Sub AppStart (Args() As String)
    varmaps.Initialize
    varmaps.Put("gs_appver", gs_appver)
    varmaps.Put("gs_appname", gs_appname)
    varmaps.Put("gs_appbuild", gs_appbuild)
    
    Log(VarVal("gs_appver"))
    Log(VarVal("gs_appname"))
    Log(VarVal("gs_appbuild"))
End Sub


Sub VarVal (Key As String) As Object
    Return varmaps.Get(Key)
End Sub

William Lancee · Dec 30, 2023

@aeric
Your solution works also with other simple types: Int Float Double Boolean etc.
A very interesting trick. How did you discover it?

@ilan
Perhaps the OP is working on some kind of scripting and wants to ask the user to enter a variable name.
Then use that string to retrieve the value.

@LucaMs (4 more posts to 30,000. You can do it before 2024!)
I believe you liked the solution in the link referenced in #5 above.
https://www.b4x.com/android/forum/t...he-name-of-a-variable-array.58197/post-366504

William Lancee · Dec 30, 2023

You can also use CallSub(Me, "GET_" & varname) to convert a string to a value

B4X:

Sub GET_gs_appname As String
    Return gs_appname
End Sub

hung · Jan 2, 2024

aeric said:

Of course such function doesn't exist in B4A or else you can already use it.

With B4XPages, I can create the function.

Note: Only valid for String variables.

B4X:

Sub Class_Globals
    Private Root As B4XView
    'Private xui As XUI
    Private varmaps As Map
    Private gs_appver As String = "2312xx"       'ignore
    Private gs_appname As String = "App name"    'ignore
End Sub

Public Sub Initialize
'    B4XPages.GetManager.LogEvents = True
    varmaps.Initialize
End Sub

Private Sub B4XPage_Created (Root1 As B4XView)
    Root = Root1
    Root.LoadLayout("MainPage")
    GenerateVarMaps
End Sub

Sub ShowAll
    ToastMessageShow(varval("gs_appver"), True)
    ToastMessageShow(varval("gs_appname"), True)
End Sub

Private Sub varval (key As String) As String
    Return varmaps.Get(key)
End Sub

Private Sub GenerateVarMaps
    Dim strMe As String = Me
    Dim Fields() As String = Regex.Split2(",", Regex.MULTILINE, strMe.SubString2(1, strMe.Length-1))
   
    For Each Field As String In Fields
        Dim ExcludeList As List = Array("b4xcollections", "b4xpages", "main", "root", "starter", "xui")
        If Field.Contains("=") Then
            Dim KeyValue() As String = Regex.Split("=", Field)
            KeyValue(0) = KeyValue(0).Trim
            KeyValue(1) = KeyValue(1).Trim
            If ExcludeList.IndexOf(KeyValue(0)) < 0 Then
                varmaps.Put(KeyValue(0), KeyValue(1))
            End If
        End If
    Next
End Sub

Private Sub Button1_Click
    ShowAll
End Sub

This works for sure. But unfortunately changing all variables into map means rewrite everything. So need other solutions.

hung · Jan 2, 2024

William Lancee said:
You can also use CallSub(Me, "GET_" & varname) to convert a string to a value

B4X:

Sub GET_gs_appname As String Return gs_appname End Sub

This is close but that refers to putting a lot of Select Case into a lot of functions.

ilan · Jan 2, 2024

why don't you use the variable directly?

B4X:

Sub Process_Globals
    Private gs_appver As String = "2312xx"
    Private gs_appname As String = "App name"
End sub

Sub Showall()
    ToastMessageShow(gs_appver, True)
    ToastMessageShow(gs_appname, True)
End sub

aeric · Jan 2, 2024

hung said:
changing all variables into map means rewrite everything

I don't understand why you said so.

What are required:
1. Add the GenerateVarMaps sub into your B4XPage
2. Declare varmaps as Map
3. Access it

If you mean you need to convert your B4A app (Default template) to using B4XPages, then there are indeed some works.

hung · Jan 2, 2024

Thank you all for the responses, especially @aeric.

Here is the use case.

I have an app with webview allowing javascript interface CallSub. The app has many variables for different purposes. I want to allow the webpage (somewhere in internet) loaded inside the webview ( webview.loadurl() ) to callback via javascript interface to get the variable value then submit webpage hence to webserver.

If we write one function for a variable that will mean many callback functions that increases apk size a lot. Or I could use one callback function with many Select Case to return variable values by something like case "gs_appver" return gs_appver. But it is inflexible and every time when we need one more variable, both app and webpage need to update program.

or, considering the app as a client browser, the online webpage as the url somewhere in internet. The idea is to allow webpage get value of any variables stored inside the app. The app is not going to change for next one to two years but our webpage could change at any minutes to get what we want.

aeric · Jan 2, 2024

hung said:
Thank you all for the responses, especially @aeric.

Here is the use case.

I have an app with webview allowing javascript interface CallSub. The app has many variables for different purposes. I want to allow the webpage (somewhere in internet) loaded inside the webview ( webview.loadurl() ) to callback via javascript interface to get the variable value then submit webpage hence to webserver.

If we write one function for a variable that will mean many callback functions that increases apk size a lot. Or I could use one callback function with many Select Case to return variable values by something like case "gs_appver" return gs_appver. But it is inflexible and every time when we need one more variable, both app and webpage need to update program.

or, considering the app as a client browser, the online webpage as the url somewhere in internet. The idea is to allow webpage get value of any variables stored inside the app. The app is not going to change for next one to two years but our webpage could change at any minutes to get what we want.

Maybe there is a better way to rewrite the Select Case.

hung · Jan 2, 2024

William Lancee said:
@aeric
Your solution works also with other simple types: Int Float Double Boolean etc.
A very interesting trick. How did you discover it?

@ilan
Perhaps the OP is working on some kind of scripting and wants to ask the user to enter a variable name.
Then use that string to retrieve the value.

@LucaMs (4 more posts to 30,000. You can do it before 2024!)
I believe you liked the solution in the link referenced in #5 above.
https://www.b4x.com/android/forum/t...he-name-of-a-variable-array.58197/post-366504

JordiCP's reply on #8 might be solution for me. I will try that out. Thank you, William.

hung · Jan 2, 2024

hung said:
JordiCP's reply on #8 might be solution for me. I will try that out. Thank you, William.

Excellent! This works well. Thank you all for the insight. And to JordiCP who might not know this yet.
In b4x,

B4X:

...
wve.addJavascriptInterface(wv_home, "b4xcallback")
wv_home.Loadurl("....abc.html")
...
' get system variables, e.g. gs_appver
Sub getsysvar(argvar As String) As String
    Dim rslt As String
    Dim jo As JavaObject
    jo.InitializeContext
    jo = jo.InitializeNewInstance(Application.PackageName & ".main",Null)
    rslt = jo.GetField("_" & argvar)
    Return rslt
End Sub

In abc.html

B4X:

<button onclick="document.getElementById('idfld').value=b4xcallback.CallSub('getsysvar', false, 'gs_appver');">Get Appver</button>
<button onclick="document.getElementById('idfld').value=b4xcallback.CallSub('getsysvar', false, 'str_hellothere');">Get Hello There</button>

Android Question Get variable value by string of name

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