HOW TO - Declare variable with initial value

[palanolho]

Greetings everyone...

I know that this may be a noob question but...

In other programming languages, we can declare a variable and immediately set an initial value. For instances we are setting the default app settings and we would do something like

Code: Select all

var defaultColor = "blue";
var defaultPath = "c:\my directory"
var defaultWidth = 100
var defaultHeight = 200

How can I do such sing on a stack? basically this is a stack that I'm using as a Code Library

Many thanks in advance
- Miguel

[FourthWorld]

In LiveCode it's not necessary to explicitly declare variables so you can just put values into them and you're off and running.

[palanolho]

I understand that, but how can I do this if I want to do this? lets say that I want to define the defaults of my application?

many thanks
- Miguel

[Simon]

Hi Miguel,
Look up "local" in the dictionary.

Simon

[palanolho]

OK, maybe I'm not explaining myself correctly. I'll try another way.

using my first example, could I do the following on the root of my stack (e.g., outside a function or handler)

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-- VARIABLES
local defaultColor = "blue";
local defaultPath = "c:\my directory"
local defaultWidth = 100
local defaultHeight = 200

-- FUNCTIONS AND HANDLERS
on mouseup
	answer "hello world
end mouseup

many thanks

[Simon]

Do you mean:
on mouseUp
answer defaultColor
end mouseUp
and you would get "blue"?

Simon

[palanolho]

Exactly. Or accessing this variable from another stack to get the variable value

[Simon]

Ahhh

Or accessing this variable from another stack

You probably want to use a "global" variable.
Most people here will tell you a "custom property" is the "right" way to go, but for a beginner I think "global" is easier to understand.
In your stack script

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global defaultColor = "blue";
global defaultPath = "c:\my directory"
global defaultWidth = 100
global defaultHeight = 200

Now here is the thing that people mess up on:

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global defaultColor -- This must be declared everywhere you use it
on mouseUp
answer defaultColor
end mouseUp

but do spend some time figuring out how to use custom properties you may find them more to your liking.

Simon

[dunbarx]

In LiveCode, there are a few types of "standard" (there are other special ones) variables. They may be declared outside of handlers, but cannot be populated outside of handlers:

1- A local variable, declared and loaded when it is created:

on mouseUp
put something into yourVariable -- declared and populated. available only within the handler
answer yourVariable
end mouseUp

2- A script local variable, declared generally at the top of the script but outside and above any handler that might use it:

local yourVariable
on mouseDown
put something into yourVariable -- declared above, populated here, available to all handlers in the script
end mouseDown

on mouseUp
answer yourVariable -- you will get the contents
end mouseUp

3- A global variable, declared anywhere, and available in any script in any stack in the current session:

global globVar
on mouseUp
put 6 into globVar -- now available in any handler in any script that declares it
end mouseUp

Only takes a little getting used to.

Craig Newman

[Simon]

put 6 into globVar

Yeah, I think that's the way I do it not globVar = 6

Declare the globals at the top of the stack script

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global defaultColor,defaultPath...

on openStack
put "blue" into defaultColor
put "c:\..." into defaultPath
etc.
end openStack

Simon

[palanolho]

Thank you very much to all.

Now I'm clarified.

cheers!
- Miguel