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LCB Module Level Variables

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LiveCode Builder Module Level Variables

A variable definition defines a module-scope variable. In a widget module, such variables are per-widget (i.e. instance variables). In a library module, there is only a single instance (i.e. a private global variable). Module-scope variables in LCB are similar to script local variables in LiveCode Script.

The syntax for declaring variables is

[private | public] variable <variableName> [as <type>]
 The type specification for the variable is optional, if it is not specified the type of the variable is optional any meaning that it can hold any value, including being nothing.

Variables whose type has a default value are initialised to that value at the point of definition. The default values. For a list of default values see the ‘Variables’ section of the LiveCode Builder Language Reference Guide. The guide can be found under the Guides tab of the Dictionary or in the Additional Resources section of the course.

Variables whose type do not have a default value will remain unassigned and it is a checked runtime error to fetch from such variables until they are assigned a value.

Variable declararions

In this widget we will use 1 module level variable to store the value of the rotation property of the widget.

The value of the rotation property must be a number so we define the type as such.

The variable will be an module level instance variable, so we prepend the variable name with a lower case ‘m’ to make it easily identifiable as such.

Add the variable definition to the widget code.

widget community.livecode.elanorb.rotatedtext

use com.livecode.canvas
use com.livecode.widget
use com.livecode.engine
use com.livecode.library.widgetutils

metadata title is "Rotated Text"
metadata author is "Elanor Buchanan"
metadata version is "1.0.0"

variable mRotation as Number

end widget

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Lessons Status
1 - Hello World Library
  • Introduction
  • Installing a Text Editor
  • Creating an LCB library
  • LCB library definition
  • LCB handler definitions
  • Compiling and testing a library in LiveCode
  • LCB metadata
  • Installing an LCB Library
  • Packaging and sharing an LCB library
  • Including an LCB library in a standalone
  • Conclusion
2 - Extended Hello World Library
  • Introduction
  • Explicit Types
  • LCB Lists and Arrays
  • Type Conversion between LCB and LiveCode Script
  • Using Explicit Typing in the Library
  • Passing Parameters to the Library
  • Using Lists in the Library
  • Documenting the Library
  • Browsing the Documentation
  • Conclusion
3 - Rotated Text Widget
  • Introduction
  • Defining a Widget
  • LCB Module Level Variables
  • Widget Properties
  • Widget Handlers
  • LCB Canvas Operations
  • Compiling and Testing the Widget
  • Installing the Widget and adding it to a Stack
  • Including the Widget in a Standalone
  • Conclusion
4 - Extended Rotated Text Widget
  • Introduction
  • Integrating Properties
  • Accessing LiveCode Control Properties
  • Handling Mouse Events
  • Saving and Loading Widgets
  • Read Only Properties
  • Documenting the Widget
  • Conclusion
5 - Pie Chart Widget
  • Introduction
  • Planning the Widget
  • Widget Properties
  • The OnCreate Handler
  • The OnPaint Handler
  • Responding to Mouse Events
  • Saving and Loading the Widget
  • Installing and Including the Widget in a Standalone
  • Documenting the Widget
  • Conclusion
6 - Modifying the Line Graph Widget
  • Introduction
  • Duplicating the Line Graph Widget
  • Additional Color Properties
  • Filling the area below the line
  • Adding graph marker mouse events
  • Conclusion
7 - Additional Resources
  • Extending LiveCode Guide
  • LiveCode Builder Language Reference
  • LiveCode Builder Style Guide
  • LiveCode Documentation Format
 

LCB Source

LCB Source
 

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