A totally n00b question, if you please?

[DDoutelMS]

Hi folks,

New to NSIS, and I have what no doubt is a totally dumb syntactical question.

If I have this definition of a constant:

code:
!define PRODUCT_NAME "Flibbin"

Under what conditions would I need this construct, with the ${} to reference the value, as in:

code:
Name "${PRODUCT_NAME}"

or this definition of a variable:

code:
Var bInstallingForChrome

Under what conditions would I need the ${} construct to reference the variable, when I can do something like:

code:
StrCpy $bInstallingForChrome "1"

So, purely a syntactical question; what purpose does the ${} construct serve in NSIS script?

Thanks in advance!
DDoutelMS

[JasonFriday13]

Originally Posted by DDoutelMS

Hi folks,

New to NSIS, and I have what no doubt is a totally dumb syntactical question.

If I have this definition of a constant:

code:
!define PRODUCT_NAME "Flibbin"

Under what conditions would I need this construct, with the ${} to reference the value, as in:

code:
Name "${PRODUCT_NAME}"

Always. !define is a compile time command. The only time you don't need ${} is when using the compiler commands (starts with !), so !undef PRODUCT_NAME is correct.

Originally Posted by DDoutelMS

or this definition of a variable:

code:
Var bInstallingForChrome

Under what conditions would I need the ${} construct to reference the variable, when I can do something like:

code:
StrCpy $bInstallingForChrome "1"

Never. Var is a runtime command, so you should always use $ to reference it. If you use ${}, you should get a compiler error about it not being defined.

[DDoutelMS]

Thanks, Jason! I think that covers it! Much appreciated.

DDoutelMS

[JasonFriday13]

Forgot to mention that you can nest defines as well, like this:

code:
!define bar "test"

!define foo "${bar} string"



Function .onInit

  MessageBox MB_OK "${foo}" ; should show "test string" without quotes.

FunctionEnd

A more dynamic example:

code:
Function .onInit

!define foo "first"

!define bar "second"

!define string "${foo},${bar}"

  MessageBox MB_OK "${string}" ; should show "first,second" without quotes.

!undef string

!define string "${bar},${foo}"

  MessageBox MB_OK "${string}" ; should show "second,first" without quotes.

FunctionEnd

[DDoutelMS]

Originally Posted by JasonFriday13

Forgot to mention that you can nest defines as well, like this:

code:
!define bar "test"

!define foo "${bar} string"



Function .onInit

  MessageBox MB_OK "${foo}" ; should show "test string" without quotes.

FunctionEnd

A more dynamic example:

code:
Function .onInit

!define foo "first"

!define bar "second"

!define string "${foo},${bar}"

  MessageBox MB_OK "${string}" ; should show "first,second" without quotes.

!undef string

!define string "${bar},${foo}"

  MessageBox MB_OK "${string}" ; should show "second,first" without quotes.

FunctionEnd

Ah, see, I think this is what's got me confused; I just don't know what the ${} actually does! Is there a "nutshell" answer for what purpose they serve? Toldja I'm a total NSIS n00b...

[Anders]

${define}

$variable

$(langstring)

[DDoutelMS]

Originally Posted by Anders

${define}

$variable

$(langstring)

So I read this as:

If I'm referencing the value of a constant, I should use ${}; if I'm referencing a variable, all I need is the $, and if I'm using a langstring, I need $(); is that correct?

Thanks again in advance!
DDoutelMS

[LoRd_MuldeR]

You can think of ${foo} as something that will be replaced with a fixed string at the moment when your .nsi script file gets compiled to an .exe file. So, yes, it's pretty much a constant. Note that you can also pass the "/Dfoo=something" parameter to makensis.exe to set the value of ${foo}. So it's useful for things you need to set at compile time. It's also similar to the preprocessor defines in C and C++.

Conversely, $X is a variable. So its value can still be changed at the time when your installer is actually running, e.g. via StrCpy. NSIS has the variables $0 to $1 as well as $r1 to $r9 that are available for general usage. Pretty much like "registers" in assembly language. Furthermore, there are special variables like $DESKTOP and so on that NSIS will fill with the corresponding path at runtime. You can also define your own variables via var something. Last but not least, $(bar) is for translatable strings that will be loaded from language file.

See also:
http://nsis.sourceforge.net/Docs/Chapter4.html#varother

[DDoutelMS]

Originally Posted by LoRd_MuldeR

You can think of ${foo} as something that will be replaced with a fixed string at the moment when your .nsi script file gets compiled to an .exe file. So, yes, it's pretty much a constant. Note that you can also pass the "/Dfoo=something" parameter to makensis.exe to set the value of ${foo}. So it's useful for things you need to set at compile time. It's also similar to the preprocessor defines in C and C++.

Conversely, $X is a variable. So its value can still be changed at the time when your installer is actually running, e.g. via StrCpy. NSIS has the variables $0 to $1 as well as $r1 to $r9 that are available for general usage. Pretty much like "registers" in assembly language. Furthermore, there are special variables like $DESKTOP and so on that NSIS will fill with the corresponding path at runtime. You can also define your own variables via var something. Last but not least, $(bar) is for translatable strings that will be loaded from language file.

See also:
http://nsis.sourceforge.net/Docs/Chapter4.html#varother

Excellent explanation! Thanks , LoRd_MuldeR, for taking the time!

DDoutelMS