Can Data Classes Contain Methods for Validation?

datavalidation

OK, say I have a data class for a user:

public class User {
private String firstName;
private String lastName;
private long personCode;
private Date birthDate;
private Gender gender;
private String email;
private String password;

Now let's say I want to validate email, whether names are not empty, whether birth date is in normal range, etc. Can I put that validation method in this class together with data? Or should it be in UserManager which in my case handles the lists of these users?

Best Answer

You can definitely validate these attributes in your setters(). Unlike getters which are meant to return values, setters are methods to assign a value via an argument/parameter.

Ideally, i would advise you to write separate methods and have their return values true or false. for validating your class attributes particularly when the validation is quite extensive.

Examples:

bool validateEmail(string email) {

}

bool validatePassword(string pwd) {

}

bool validateBirthdate(date dob) {

}

I would rather advise to validate your class attributes in the Business Logic Layer. I wonder if you know about the software logical architecture. FYI: BLL

Also if you have a database then it is best to have them validated there via constraints.

Related Solutions

C# Validation – Best Way of Validating Class Properties

If I needed to input data and capture errors, I would probably do something more like:

public class Employee
{
    public int EmpID { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Salary { get; set; }
}

public class ErrorEmployee : Employee
{
    public string[] ErrorReason { get; set; }
}

Read CSV file row by row
For each element i.e EmpId, FirstName... etc do the required validations by calling individual methods having validation logic. eg: public bool ValidateIsDecimal(string value) { } public bool ValidateIsEmpIdExists(string value) { } etc
If valid, fill corresponding property of "Employees" class. Add this Class to Employees collection (eg: List)
If NOT VALID, fill "ErrorReason" property, with appropriate reason as to what caused the validation to fail.(eg: Required filed was missing or datatype is not decimal etc) Add this Class to ErrorEmployees collection (eg: List)

I wouldn't want to pollute the regular Employee (singular, use the plural for a collection of them) object with error messages. As in the note above, check out the FluentValidation library for your validation and capture a list of errors rather than just the first found.

Domain Model, validation, and pushing errors to the model

I would create a domain service responsible for validating the uniqueness of the category. In my solution domain defines the interface of the service, infrastructural part implements it using a database.

Please also take a look at https://stackoverflow.com/questions/516615/validation-in-a-domain-driven-design.

Best Answer

Related Solutions

C# Validation – Best Way of Validating Class Properties

Domain Model, validation, and pushing errors to the model

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