DDD Validation Example:

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Problems I'm trying to solve:

• Code must be readable, therefore big functions and methods should not appear when we're increasing number of validation rules. Clean code
• Domain layer must be isolated from other layers Clean architecture
• Entity must never enter invalid state Always-Valid domain model principle from DDD
• Application layer should have an opportunity to pass properly structured validation errors to presentation layer.
• All possible validation error should be easily displayable somewhere (for example, QA engineer might need all possible not 500-th errors which might appear on one every endpoint)

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