Simple way to implement a string interpolation in AppleScript

Question

I want to implement a string interpolation in AppleScript, similar to the basic python implementation. For example in python:

print('Hello {}'.format('earth')) #> Hello World

In AppleScript, how do I implement the format handler?

to format(theString, {tokens})
    -- TODO
end format

log format("Hello {}", {"Apple"})  -- # Hello Apple

vadian · Accepted Answer · 2021-03-15 10:55:38Z

2

The python syntax and the AppleScript/ObjC syntax are not compatible.

If you are talking about only one argument there is a simple solution with help of NSString's stringWithFormat

use AppleScript version "2.5"
use framework "Foundation"
use scripting additions

to format(theString, tokens)
    return (current application's NSString's stringWithFormat_(theString, tokens)) as text
end format

log format("Hello %@", "Apple") -- # Hello Apple

For more arguments you have to use an if - else clause to convert the argument array to the ObjC va_list

to format(theString, tokens)
    set numberOfArguments to count tokens
    if numberOfArguments = 1 then
        return (current application's NSString's stringWithFormat_(theString, item 1 of tokens)) as text
    else if numberOfArguments = 2 then
        return (current application's NSString's stringWithFormat_(theString, item 1 of tokens, item 2 of tokens)) as text
    else if numberOfArguments = 3 then
        return (current application's NSString's stringWithFormat_(theString, item 1 of tokens, item 2 of tokens, item 3 of tokens)) as text
    else
        error "Invalid number of arguments"
    end if
end format

log format("Hello I'm %@ and I'm %@ years old", {"John", 25}) -- # Hello I'm John and I'm 25 years old

edited Mar 15, 2021 at 10:55

answered Mar 15, 2021 at 10:33

vadian

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3 Comments

user3579815 Over a year ago

Thank you for your sample code. TBH, I'm not yet ready to try the ObjC, at least not yet, I'll give it try and see if I can build from there. My initial idea was to find and replace occurences of {} in the string, similar to when I implemented a find and replace. Just worried it won't be a trivial implementation.

user3579815 Over a year ago

I'm getting error "NSString doesn’t understand the “stringWithFormat_” message." do I need to install/configure anything to make it work?

vadian Over a year ago

You have to put always the three (at least the first two) use lines into your script when dealing with AppleScriptObjC. Parsing {} is not trivial in AppleScript.

user3579815 · Accepted Answer · 2021-03-18 09:23:49Z

1

I wrote a simple implementation using sed

to format(theString as text, theTokens as list)
    if class of theTokens is text then set theTokens to {theTokens}
    set builtString to theString
    repeat with nextToken in theTokens 
        set builtString to do shell script "echo '" & builtString & "' | sed 's/{}/" & nextToken & "/'"
    end repeat
    return builtString  
end format

I have tested it with only 2 scenarios, I'm sure there are more I haven't covered:

format("Hello {}", "baby") -- # Hello baby
"Hello {}, how are you {}", {"baby", "mom"}  -- # Hellow baby, how are you mom

answered Mar 18, 2021 at 9:23

user3579815

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