Summerize assert in dart constructors-CodePudding

I have multiple constructors in the same class and they have many assert functions which is the same for all constructors. For example a class Foo have 2 constructors:

Foo({...some params}):assert(conditionA),assert(conditionB),assert(conditionC);
Foo.fromForm({...some params}):assert(conditionA),assert(conditionB),assert(conditionC);

Is there any ways that i can group the assert and share to the two constructors?

CodePudding user response：

You can share the assertions by making your named constructor call the unnamed one.

Let's say I have defined my class Foo like this:

class Foo {
  final int? paramA;
  final bool? paramB;

  Foo({
    this.paramA,
    this.paramB,
  })  : assert(
          (paramA == null && paramB != null) ||
              (paramA != null && paramB == null),
          'You cannot use both paramA and paramB',
        ),
        assert(
          paramA == null || paramA > 0,
          'When specified paramA must be superior to 0',
        );
}

I can have an assertion error when doing the following:

Foo(paramA: -1); // Assertion failed: "When specified paramA must be superior to 0"

Foo(paramA: 1, paramB: false); // Assertion failed: "You cannot use both paramA and paramB"

Now if I declare my secondary constructor as follow:

class Foo {
  // ...
  
  Foo.fromForm(int param) : this(paramA: param);
}

When using this() I define that my Foo.fromForm constructor will call my base unnamed Foo constructor and will beneficiate from its assert.

This could also work by using an abstract class:

abstract class BaseFoo {
  BaseFoo({
    required int? paramA,
    required bool? paramB,
  }) : assert(
          (paramA == null && paramB != null) ||
              (paramA != null && paramB == null),
          'You cannot use both paramA and paramB',
        ),
        assert(
          paramA == null || paramA > 0,
          'When specified paramA must be superior to 0',
        );
}

class Foo extends BaseFoo {
  final int? paramA;
  final bool? paramB;

  Foo({
    this.paramA,
    this.paramB,
  }) : super(paramA: paramA, paramB: paramB);

  // You can also call this()
  Foo.fromForm(int param)
      : paramA = param,
        paramB = null,
        super(paramA: param, paramB: null);
}