Question

Is it possible to predefine constant or variable for an AppleScript in cocoa application?
in other words is the function “addConstantToAppleScript” (used in the following code) definable?

addConstantToAppleScript("myText", "Hello!");
char *src = "display dialog myText";
NSString *scriptSource = [NSString stringWithCString:src]; 
NSAppleScript *appleScript = [[NSAppleScript alloc] initWithSource:scriptSource];
NSDictionary *scriptError = [[NSDictionary alloc] init];
[appleScript executeAndReturnError:scriptError];

thanks.

Answer 1

If you want to prepend an NSDictionary of key/value pairs to the beginning of an NSString containing AppleScript you could use something like the following function. Personally I would do this as a category on NSString but you have asked for a function.

NSString *addConstantsToAppleScript(NSString *script, NSDictionary *constants) {
    NSMutableString *constantsScript = [NSMutableString string];

    for(NSString *name in constants) {
        [constantsScript appendFormat:@"set %@ to \"%@\"\n", name, [constants objectForKey:name]];
    }   

    return [NSString stringWithFormat:@"%@%@", constantsScript, script];
}

This function converts the key/value pairs to AppleScript statements of the form set <key> to "<value>". These statements are then added to the front of the supplied script string. The resulting script string is then returned.

You would use the above function as follows:

// Create a dictionary with two entries:
//     myText = Hello\rWorld!
//     Foo    = Bar
NSDictionary *constants = [[NSDictionary alloc ] initWithObjectsAndKeys:@"Hello\rWorld!", @"myText", @"Bar", @"Foo", nil];

// The AppleScript to have the constants prepended to   
NSString *script = @"tell application \"Finder\" to display dialog myText";

// Add the constants to the beginning of the script 
NSString *sourceScript = addConstantsToAppleScript(script, constants);

// sourceScript now equals
//     set Foo to "Bar"
//     set myText to "Hello\rWorld!"
//     tell application "Finder" to display dialog myText

NSAppleScript *appleScript = [[NSAppleScript alloc] initWithSource:sourceScript];