ByRef - Nothing happens Topic is solved

[Albireo]

I tried to return an array and three variables from a function.
To succeed with this, I intended to use ByRef
All of these variables are normally empty before the function is used,
Thought to provide a default value for these variables with ByRef.

I wrote this test program to show my wishes .:

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funcByRef()
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 1 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	aVar[1] .: " aVar[1]
)

Var3 = 100
funcByRef(,,Var3)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 2 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	aVar[1] .: " aVar[1]
)




ExitApp


funcByRef(Var1 := "Def", ByRef Var2 := "" , ByRef Var3 = 10)
{	Var2 = inside the function
	Var3 := Var3 * 10
	
	aVar := {}
	aVar.Push("Test1")
	aVar.Push("Test2")
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	"    Inside the function() `n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		aVar[1] .: " aVar[1]
	)
	Return % aVar
}

Something I've misunderstood with ByRef?

Also tried ByRef aVar := {} but it didn't AHK like at all

[wolf_II]

I tried to return an array and three variables from a function.

You succeeded in returning an array from the function, but in your test there is no catcher.
To catch the "rebouncing" return value, you write:

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aVar := funcByRef()

[Albireo]

comments from wolf_II

... but in your test there is no catcher.
To catch the "rebouncing" return value, you write:

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aVar := funcByRef()

Of course! (I forgot it) - Thanks!
First I tried (as I said) to also include the array with ByRef like this .:

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funcByRef(Var1 := "Def", ByRef Var2 := "" , ByRef Var3 = 10, ByRef aVar := {})

But I got an error message.... I gave up to use ByRef with the array aVar
Var2 never gets any value from FuncByRef().
After the second case Var3 seems to work as desired. (after the first case I got nothing...)
What am I doing wrong?

In the helpfile for ByRef it was an example .:

ByRef from AHK helpfile

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returnByRef(A,B,C)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%, % A "," B "," C

returnByRef(ByRef val1, ByRef val2, ByRef val3)
{
    val1 := "A"
    val2 := 100
    val3 := 1.1
    return
}

It's almost the same as mine example, but they don't have any default value.
In the help file it says .: (exactly what I want)

Since return can send back only one value to a function's caller, ByRef can be used to send back extra results. This is achieved by having the caller pass in a variable (usually empty) in which the function stores a value.

Under ByRef / optional parameters the helpfile says .:

ByRef parameters also support default values; for example: MyFunc(ByRef p1 = ""). Whenever the caller omits such a parameter, the function creates a local variable to contain the default value; in other words, the function behaves as though the keyword "ByRef" is absent.

Have I understood correctly, What I am trying to do will not work (is impossible in AHK)?

A little updated test program, also with examples from the AHK help file

Code: Select all

#NoEnv  ; Recommended for performance and compatibility with future AutoHotkey releases.

aVar := funcByRef(, Var2)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 1 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	aVar[1] .: " aVar[1]
)
Var1 =
Var2 = 
Var3 = 100

aVar := funcByRef(, Var2, Var3)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 2 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	aVar[1] .: " aVar[1]
)


ReturnByRef(A,B,C)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%, % "AHK -example ByRef .: `n`n"A "," B "," C


ExitApp

ReturnByRef(ByRef val1, ByRef val2, ByRef val3)
{
    val1 := "A"
    val2 := 100
    val3 := 1.1
    Return
}


funcByRef(Var1 := "Def", ByRef Var2 = "" , ByRef Var3 := "10")
{	Var2 = inside the function
	Var3 := Var3 * 10
	
	aVar := {}
	aVar.Push("Test1")
	aVar.Push("Test2")
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	"    Inside the function() `n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		aVar[1] .: " aVar[1]
	)
	Return % aVar
}

Is this possible to solve in another way?

[hd0202]

1) you did not mark the relevant part of the help text:

ByRef parameters also support default values; for example: MyFunc(ByRef p1 = ""). Whenever the caller omits such a parameter, the function creates a local variable to contain the default value; in other words, the function behaves as though the keyword "ByRef" is absent..

This means: you must give a parameter to the function for each value you want returned "Byref"

2) you cannot give an array as default value, so you got an error message. use instead ""

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funcByRef(Var1 := "Def", ByRef Var2 = "" , ByRef Var3 := "10", Byref Var4 := "")

3) MsgBox does not show the content of an object automatically, so you must check for it

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If isobject(var...)

I connect my version of your last test code:

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#NoEnv  ; Recommended for performance and compatibility with future AutoHotkey releases.
funcByRef(, Var2, , Var4)
if isobject(var4)
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	"`tResult test 1 with object in var4, but without catcher`n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		Var4 .: is object
		aVar[1] .: " aVar[1]
	)

aVar := funcByRef(, Var2, , Var4)
if isobject(var4)
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	"`tResult test 1 with object in var4`n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		Var4 .: is object
		aVar[1] .: " aVar[1]
	)

MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 1 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	Var4 .: " Var4 "
	aVar[1] .: " aVar[1]
)

Var1 =
Var2 = 
Var3 = 100

aVar := funcByRef(, Var2, Var3)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
( LTrim
 %	"`tResult test 2 `n
	Var1 .: " Var1 "
	Var2 .: " Var2 "
	Var3 .: " Var3 "
	aVar[1] .: " aVar[1]
)


ReturnByRef(A,B,C)
MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%, % "AHK -example ByRef .: `n`n"A "," B "," C


ExitApp

ReturnByRef(ByRef val1, ByRef val2, ByRef val3)
{
    val1 := "A"
    val2 := 100
    val3 := 1.1
    Return
}


funcByRef(Var1 := "Def", ByRef Var2 = "" , ByRef Var3 := "10", Byref Var4 := "")
{	Var2 = inside the function
	Var3 := Var3 * 10
	
	aVar := {}
	aVar.Push("Test1")
	aVar.Push("Test2")
	var4 := avar
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	"    Inside the function() `n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		Var4 .: " Var4 "
		aVar[1] .: " aVar[1]
	)
	Return % aVar
}

Hubert

[Albireo]

Thanks!
Now it works to send an array from a function using ByRef
The question remains .: How to use a default value at the same time you want to use ByRef

But… (only look on the "Array" Var4 / aVar4)
Whats the difference by this two functions? .:

• funcByRef(FromRow, Info, ByRef Var4 := "")
• funcByRef(FromRow, Info, ByRef Var4)

I can (as I see it) never give a default value in this case.
Give a value to a variable that will later be converted to an array, it felt pointless.

TestScript Var4 / aVar4

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#NoEnv  ; Recommended for performance and compatibility with future AutoHotkey releases.
#SingleInstance Force
SendMode Input  ; Recommended for new scripts due to its superior speed and reliability.

; Test aVar4 - Works (inside and outside the function)
; Note .: The array name is not the same, (inside and outside the function)
Line := A_LineNumber + 2
Info = - Test of aVar4 (Row .: %Line% )`nfuncByRef(Line, Info, aVar4)
aVar := funcByRef(Line, Info,aVar4)
Gosub Result

MsgBox ,,, Ready!, 2
ExitApp


Result:
	if isobject(aVar4)
		Info1 = It works!
	else
		Info1 = It doesn't work!
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	%	"Result OUTSIDE the function()
		" Info "`n
		aVar4[2] .: " aVar4[2] " - " Info1 "
		aVar[1] .: " aVar[1]
	)
Return

funcByRef(FromRow, Info, ByRef Var4 := "")
{	
	funcName = funcByRef()
	
	; Var2 = From inside %FuncName%
	Var3 := Var3 * 10
	
	aVar := {}
	aVar.Push("Test1")
	aVar.Push("Test2")
	Var4 := aVar
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	" - INSIDE .: " funcName "
		" Info "`n
		Var4[2] .: " Var4[2] "
		aVar[1] .: " aVar[1]
	)
	Return % aVar
}

---

We can look at three examples of handling .: Var3 - The function .:
funcByRef(FromRow, Info, Var1 := "Only local", ByRef Var2 := "Default Value" , ByRef Var3 := "10", ByRef Var4 := "")

a) Var3 has no value before funcByRef(Line, Info,,,Var3 ,aVar4)
It works? inside and outside the function (do not use the default value) - I got nothing as result.

b) Var3 is set before the function call like this.
Var3 = 100
aVar := funcByRef(Line, Info,,,Var3 ,aVar4)
Yes! ByRef works, but does not use the default value.

c) Var3 is not in the function call, like this .:
aVar := funcByRef(Line, Info,,,,aVar4)
Yes/No! default value works (in the function), but does not return some result to the main program.

AHK -test Var3 ByRef / DefaultValue

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#NoEnv  ; Recommended for performance and compatibility with future AutoHotkey releases.
#SingleInstance Force
SendMode Input  ; Recommended for new scripts due to its superior speed and reliability.

; Test aVar4 - Works (inside and outside the function)
; Note .: The array name is not the same, (inside and outside the function)
Line := A_LineNumber + 2
Info = - Test of aVar4 (Row .: %Line% )`nfuncByRef(Line, Info,,,,,aVar4)
aVar := funcByRef(Line, Info,,,,aVar4)
Gosub Result


; Test Var3a - Maybe works - I got nothing as result (inside and outside the function)
Line := A_LineNumber + 2
Info = Test of Var3a `nfuncByRef(Line, Info,,,Var3 ,aVar4)
aVar := funcByRef(Line, Info,,,Var3 ,aVar4)
Gosub Result


; Test Var3b - Works (inside and outside the function) - I got 1000 as expected
Line := A_LineNumber + 3
Info = Test of Var3 `nfuncByRef(Line, Info,,,Var3 ,aVar4)
Var3 = 100
aVar := funcByRef(Line, Info,,,Var3 ,aVar4)
Gosub Result


; Test Var3c - Don't work (The result in the function is 10 and outside the function is 100) 
Line := A_LineNumber + 3
Info = Test of Var3 `nfuncByRef(Line, Info,,,Var3 ,aVar4)
Var3 = 1
aVar := funcByRef(Line, Info,,,,aVar4)
Gosub Result
MsgBox ,,, Ready!, 2
ExitApp


Result:
	if isobject(aVar4)
		Info1 = It works!
	else
		Info1 = It doesn't work!
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	%	"Result OUTSIDE the function()
		" Info "`n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		aVar4[2] .: " aVar4[2] " - " Info1 "
		aVar[1] .: " aVar[1]
	)
Return

funcByRef(FromRow, Info, Var1 := "Only local", ByRef Var2 := "Default Value" , ByRef Var3 := "10", ByRef Var4 := "")
{	
	funcName = funcByRef()
	
	; Var2 = From inside %FuncName%
	Var3 := Var3 * 10
	
	aVar := {}
	aVar.Push("Test1")
	aVar.Push("Test2")
	Var4 := aVar
	
	MsgBox ,, Row.: %A_LineNumber% -> %A_ScriptName%,
	( LTrim
	 %	" - INSIDE .: " funcName "
		" Info "`n
		Var1 .: " Var1 "
		Var2 .: " Var2 "
		Var3 .: " Var3 "
		Var4[2] .: " Var4[2] "
		aVar[1] .: " aVar[1]
	)
	Return % aVar
}

---

My conclusion .: Using ByRef and setting a Default value seems difficult/ impossible to manage at the same time.

• ByRef - can never be skipped (as I understand it)
• Variables with default values - can be skipped.

[swagfag]

Code: Select all

; Test Var3c - Don't work (The result in the function is 10 and outside the function is 100) 

wrong. inside the function Var3 is 100, and outside of it it is 1

to have a byref be optional and default initializable when passed an unitialized variable u have to do this:

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f(ByRef x := "") {
	if (x = "")
		x := "default"
}

[Albireo]

If you use the following If-sequence in the function

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if (x = "")
   x := "default"

I still don't see the big difference between the following different ByRef to the function f()
1) f(ByRef x := "") (in the example from @swagfag )
2) f(ByRef x = "") (from the AHK-helpfile for ByRef )
3) f(ByRef x) (No default value at all)
All three examples give the same result from the function f()
What I want to highlight is that the default value together with ByRef does not work.

[just me]

1) f(ByRef x := "") The expressional := assignment operator was introduced with AHK 1.1.09.
2) f(ByRef x = "") The = does the same.
3) f(ByRef x) The parameter x is mandatory here. Try to call the function as Result := f().

Default values are only used with optional parameters if you do not pass a variable or a value.