4.9 Constants
A constant is defined as a variable that can't be changed.
Constants are in ALL_UPPERCASE_WITH_UNDERSCORES (capitalized snake case)
Constants always have static final
public static final String THIS_IS_A_CONSTANT = "Constantly following the rules!";
Constants can be macros or const variables. It is highly recommended to make constants constexpr and inline as well.
#define FRC5431_CONSTANT_INOPLE 3.45921321
namespace frc5431 {
const constexpr int SPECIAL_NUMBER = 342131;
}
If using a macro as a constant, always prefix it. This prefix should be unique to your project. If you can't think one of, FRC5431_ is always good.
Functional macros follow the same rules as a normal constant. They must also be verbs.
#define FRC5431_STRINGIFY(name) #name
#define FRC5431_SUM(a, b) a + b
Functional macros with multiple lines must be wrapped in a do...while block
#define FRC5431_DO_MULTILINE() do{ ... }while(0)
REASONING: See this post for the do...while rule
Global Constants
Try to avoid non-constant global variables.
CLARIFICATION:
Global constants are static variables.
REASONING: One of the biggest factors to spaghetti code are global variables. For example, look at this code:
void doSomething(){
OtherClass.foo = "I like spaghetti";
}
...
woawver.doSomething();
void doSomething(){
bar::foo = "I like spaghetti";
}
...
doSomething()
This code is a prime example of how spaghetti code is formed. doSomething() now affects other classes and variables, so that can cause confusion to anyone using doSomething() as to why the global constant has changed it's value!
The better way to do the above code that isn't a delicious italian product is like this:
String doSomething(){
return "I am still hungry":
}
...
OtherClass.foo = woawver.doSomething()
std::string doSomething(){
return "I am still hungry";
}
...
bar::foo = doSomething();
This new technique produces completely identical code, adds more versality as now doSomething() can be used anywhere, and reduces confusion. All because you got rid of global constants!
Magic Constants
A magic constant is a literal in your code that doesn't have any meaning or explanation.
Instead of embedding literals into code, create a constant at the top of the file to reduce spatghetti code and allow for more configurability.
BAD:
NetworkTable.get("roborio-frc-5431.local");//"roborio-frc-5431.local" is a magic constant
GOOD:
private static final NETWORKTABLE_LOCATION "roborio-frc-5431.local"
...
NetworkTable.get(NETWORKTABLE_LOCATION);
You can use #define or const constexpr constants.
BAD:
NetworkTable::get("roborio-frc-5431.local");//"roborio-frc-5431.local" is a magic constant
GOOD:
#define FRC5431_NETWORKTABLE_LOCATION "roborio-frc-5431.local"
...
NetworkTable::get(FRC5431_NETWORKTABLE_LOCATION);