When
Pattern matching is done with the when keyword and a variable.
Each branch can be one or more values, a range or array of possible values, or ... for anything else (similar to default in C-type languages)
In joelang, when statements return a value.
The types of each values must match the type of the conditional variable. The return type of each branch must be the same.
// set a string variable
const size = when someNumber {
// if someNumber is 1 or 2
1, 2 -> 'small',
// between 3 and 10 (inclusive)
3 .. 10 -> 'medium',
// do stuff before, and use explicit return
11 -> {
doThing1();
doThing2();
return 'large';
},
// or call a function, whose return value will be used
12 -> someFunction(),
// any other value
... -> 'off the charts',
}
// `when`s don't have to return anything
when someNumber {
// call a function
1, 2 -> small(),
3 .. 10 -> medium(),
// fallback function to call
... -> offTheCharts(),
}