dart Control Flow Switch Case
Example
Dart has a switch case which can be used instead of long if-else statements:
var command = 'OPEN';
switch (command) {
case 'CLOSED':
executeClosed();
break;
case 'OPEN':
executeOpen();
break;
case 'APPROVED':
executeApproved();
break;
case 'UNSURE':
// missing break statement means this case will fall through
// to the next statement, in this case the default case
default:
executeUnknown();
}
You can only compare integer, string, or compile-time constants. The compared objects must be instances of the same class (and not of any of its subtypes), and the class must not override ==.
One surprising aspect of switch in Dart is that non-empty case clauses must end with break, or less commonly, continue, throw, or return. That is, non-empty case clauses cannot fall through. You must explicitly end a non-empty case clause, usually with a break. You will get a static warning if you omit break, continue, throw, or return, and the code will error at that location at runtime.
var command = 'OPEN';
switch (command) {
case 'OPEN':
executeOpen();
// ERROR: Missing break causes an exception to be thrown!!
case 'CLOSED': // Empty case falls through
case 'LOCKED':
executeClosed();
break;
}
If you want fall-through in a non-empty case, you can use continue and a label:
var command = 'OPEN';
switch (command) {
case 'OPEN':
executeOpen();
continue locked;
locked: case 'LOCKED':
executeClosed();
break;
}
