Handle unions of string constants
Use enums, unions of singletons, or unions of constants. Enum seems to be a better option out of those three.
Let's say we have a string variable named department, which can only be Finance, Engineering, or HR.
Bad Code
type Employee record {|
string name;
string department;
|};
Employee e = {name: "John Doe", department: "HR"};
- No idea what are the possible department types
- Users can specify any string value as the department. It is syntactically correct but incorrect from the scenario point of view.
Good Code
Option 1: Usage of enums
enum Department {
Finance,
Engineering,
HR
}
type Employee record {|
string name;
Department department;
|};
Employee e = {name: "John Doe", department: HR};
Note: Ballerina doesn't allow numeric enums.
Option 2: Unions of singletons
type Department "Finance"|"Engineering"|"HR";
type Employee record {|
string name;
Department department;
|};
Employee e = {name: "John Doe", department: "HR"};
Option 3: Unions of constants
const Eng = "Engineering";
const Fin = "Finance";
const HR = "HR";
type Department Eng|Fin|HR;
type Employee record {|
string name;
Department department;
|};
Employee e = {name: "John Doe", department: HR};
Conclusion
- In all three approaches, the User can't specify anything other than specified values which is good.
- Option 1: Enums is a better choice if we consider the readability and simplicity of the code.