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function

Type​

control structure

Summary​

Defines a custom function handler.

Syntax​

[private] function <functionName> [<parametersList>] 
   <statementList> 
end <functionName>

Description​

Use the function control structure to implement a custom function.

Form. The first line of a function handler consists of the word "function" followed by the function's name. If the function has any parameters, their names come after the function name, separated by commas.

The last line of a function handler consists of the word "end" followed by the function's name.

The purpose of a function is to compute a value and return it to the handler that called the function. The function's value is returned by a return control structure within the function handler.

A function handler can contain any set of LiveCode statements. Most functions contain a return statement, which returns the value to the calling handler. This example of a custom function uses two parameters and returns a string :

    function reversedName firstName,lastName
      -- firstName and lastName are parameters
      put lastName,firstName into constructedName
      return constructedName
    end reversedName

You create a custom function by writing a function handler for it. When you call the function in a handler, the function call is passed through the message path. When it reaches the object whose script contains the function handler, the statements in the handler are executed.

A custom function is called by name, just like a built-in function, as part of an expression. For example, this handler calls the custom function above:

    on mouseUp
      ask \"What is your first name?\"
      put it into firstParam
      ask \"What is your last name?\"
      put it into secondParam
      put reversedName(firstParam,secondParam) into field \"Name\"
    end mouseUp

A function can call itself. The following example calls itself to compute the factorial of an integer:

    function factorial theNumber
      if theNumber = 1 then return 1
      else return theNumber * factorial(theNumber -1)
    end factorial
note

To declare a function that is local to the script it is contained in, prefix the declaration with private. For more information about this see the dictionary entry for the private keyword.

Parameters​

NameTypeDescription

functionName

string

A string up to 65,535 characters in length.

parametersList

The parametersList consists of one or more parameter names, separated by commas.

statementList

The statementList consists of one or more LiveCode statements. The final statement is typically a return statement, which sends the value derived in the function handler back to the statement that calls the function.

Examples​

function myFunction
   return "test"
end myFunction
function cubeIt pNum
   return pNum * pNum * pNum
end cubeIt

function: functionNames, param, paramCount, result

glossary: call, caller, control structure, execute, expression, handler, message path, parameter, return, statement

keyword: dollar, end, private, string

control structure: exit, return

Compatibility and Support​

Introduced

LiveCode 1.0

OS

mac

windows

linux

ios

android

web

Platforms

desktop

server

mobile