Dart：如何将function作为参数传递

Question

Id like to call a function from another function, this is my code:

  void fooA () {
    //do something
  }
  
  void fooB (fooC) {
    fooC();
  }
  
  fooB (fooA);

Why is fooA not executed?

Answer 1

The code you provided functions:

void fooA () {
  print('hi');
}

void fooB (fooC) {
  fooC();
}

main() {
  fooB (fooA);
}

Output:

hi

However, it is better to fully type function arguments, as in:

void fooA() {
  print('hi');
}

void fooB(void Function() fooC) {
  fooC();
}

main() {
  fooB(fooA);
}

Note the fully descriptive type declaration void Function() fooC . Doing so enables the compiler to use static type checking to ensure the passed in function has the correct parameter and return types.

References

• PREFER using function type syntax for parameters.
• PREFER inline function types over typedefs.
• Dart language specification , section 20.5, "20.5 Function Types."