Handle unions of integer constants

Use unions of singletons or unions of constants. Unions of constants seem to be a better option out of those three.

Let's say we have an int variable named priority which can only be 1, 2, or 3 where 1 is the highest priority.

Bad Code

type Issue record {|
   string title;
   int priority;
|};
 
Issue issue = {title: "Incorrect input parameters", priority: 1};

• No idea what are the possible priority values
• By looking at the issue value, we can't get a sense of priority level. Whether priority 1 means the highest priority or lowest priority.
• Users can specify any int value as the priority. It is syntactically correct but incorrect from the scenario point of view.

Good Code

Option 1:Unions of singletons

type Priority 1|2|3;
 
type Issue record {|
  string title;
  Priority priority;
|};
 
Issue issue = {title: "Incorrect input parameters", priority: 1};

Option 2: Unions of constants

const HIGH = 1;
const MEDIUM = 2;
const LOW = 3;
 
type Priority HIGH|MEDIUM|LOW;
 
type Issue record {|
   string title;
   Priority priority;
|};
 
Issue issue = {title: "Incorrect input parameters", priority: HIGH};

Conclusion

• Both Options 1 and 2 restrict the users from having arbitrary integer values for priority.
• But in option 1, by looking at the priority value, we can't understand whether 1 means high or low.
• So Option 2: Unions of constants is the best option.

See Also:

• Unions