Summary - Type aliases

Combine typedef, Record and pattern matching to write a DTO system.

Summary: Type aliases

In this group you named function types with typedef and complex types with a type alias. You bundled values with a Record, unpacked them with pattern matching and produced results by pattern with a switch expression.

Now we combine them: we will name a Record with a type alias and match it with a switch expression. This shows Dart 3's data power.

Remember: an alias only names, a Record is immutable and a switch expression produces a value.

Exercise The Point DTO

Define typedef Point = (int x, int y);. In main create Point p = (3, 4);. Match p with a switch expression: (0, _) => 'on axis', (_, 0) => 'on axis', _ => 'in plane'. Print the result with print.

Show example solution

typedef Point = (int x, int y);

void main() {
  Point p = (3, 4);
  print(switch (p) {
    (0, _) => 'on axis',
    (_, 0) => 'on axis',
    _ => 'in plane',
  });
}

Test yourself

Concept matching

typedef

Names a function type
type alias

Names a complex type
Record

Value bundle
switch expression

Result by pattern
Result for Point p = (3,4)?
- on axis
- Empty
- Error
- in plane
Show answer

in plane — (3,4) is not on an axis so the _ arm runs.

Record wildcard pattern

switch (p) {
  (0, ____) => 'eksende',
  _ => 'düzlemde',
}

Show answer

switch (p) {
  (0, _) => 'eksende',
  _ => 'düzlemde',
}

Next lesson: Metadata

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