Best Practices: Variables

Notes from Code Complete 2: Chapter 10

Date Types

• Know your data types (10.1)

Declaration and Naming

• Declare all variables (turn off implicit declarations) (10.2)
• Follow naming conventions (10.2)

Initialization

• Initialize each variable as it’s declared (10.3)
• Declare and define each variable close to where it’s first used (10.3)
• Initialize working memory at the beginning of your program
• Use the compiler setting that automatically initializes all variables
• Initialize a class’s member data in its constructor
• Pay special attention to counters and accumulators – ensure that they are initialized properly and, if necessary, reinitialized each time they are used
• Check the need for reinitialization
• Check that variables are reinitialized properly in code that’s executed repeatedly
• Initialize named constants once; initialize variables with executable code
• Check input parameters for validity
• Use a memory-access checker to check for bad pointers
• Don’t assign a value to a variable until just before the value is used
• Use final or const when possible
• Use named constants (avoid magic numbers)
• Strike a conscious balance between the flexibility of late binding and the increased complexity associated with late binding

 Scope

• Ensure that variables have the smallest scope possible
• Develop the habit of declaring and initializing all data right before it’s used
• Localize References to Variables
• Keep Variables “Live” for as Short a Time as Possible
• Initialize variables used in a loop immediately before the loop rather than back at the beginning of the routine containing the loop
• Group related statements
• Break groups of related statements into separate routines
• Begin with most restricted visibility, and expand the variable’s scope only if necessary

Purpose

• Use each variable for one purpose only
• Avoid variables with hidden meanings
• Make sure that all declared variables are used

Persistence

• Write code that assumes data isn’t persistent (10.5)

Release

• Set variables to “unreasonable values” when you’re through with them (10.6)

General

• Enable and pay attention to compiler warnings

Advertisement