Invariant mixin

Design by Contract: Mixin for enforcing object invariants.

An invariant is a condition that must always be true for an object throughout its lifetime. By implementing Invariant, you declare what invariants your class maintains.

Use this mixin to:

• Document and enforce class invariants
• Catch state corruption early during development
• Ensure consistency after state-modifying operations

Example:

class BankAccount with Invariant {
  double _balance;

  BankAccount(this._balance);

  void withdraw(double amount) {
    _balance -= amount;
    checkInvariant('withdraw');
  }

  @override
  bool invariant() => _balance >= 0; // Balance must never be negative
}

1. @experimental

Properties

hashCode → int

The hash code for this object.

no setter, inherited

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

checkInvariant(String operation) → void

Asserts that the invariant is satisfied for operation.

invariant() → bool

The invariant condition that must always be true for this object.

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toString() → String

A string representation of this object.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited