Comparing Objects by Value. Part 6: Structure Equality Implementation

We have already analyzed peculiarities of structs of the .NET framework that represent Value Types when comparing objects by value – instance of structs.

Now, I am going to describe this process on a particular example to check whether it will allow us to determine the use of the object comparison by value in general and thus, to simplify a sample of comparing objects by value – class instances that represent reference types.

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Comparing Objects by Value. Part 4: Inheritance & Comparison Operators

In the previous article, we analyzed how to compare objects by value on a particular example with the Person class that includes:

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Comparing Objects by Value. Part 3: Type-specific Equals and Equality Operators

In Part 1 and Part 2, we have analyzed how to modify a class to compare objects by value.

Now, we will explore a type-specific implementation of how to compare objects by value including the IEquatable(Of T) generic interface and overload of “==” and “!=” operators.

Type-specific comparison of objects by value allows achieving:

  • a more stable, scalable and mnemonic (readable) code through overloaded operators;
  • higher performance.

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Comparing Objects by Value. Part 2. Implementation Notes of the Equals Method

In the previous article, we have reviewed a general concept of implementing a minimum set of required modifications that include overriding the Object.Equals(Object) and Object.GetHashCode() methods in order to compare class objects by value on a standard .NET framework.

Let’s consider the implementation features of the Object.Equals(Object) method so that it meets the following documentation requirement:

x.Equals(y) returns the same value as y.Equals(x).

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Comparing Objects by Value. Part 1. Beginning

It is a common fact that the .NET object model, as well as other software program platforms, allow comparing objects by reference and by value.

By default, two objects are equal if the corresponding object variables have the same reference. Otherwise, they are different.

However, in some cases, you may need to state that two objects belonging to the same class are equal if their content match in a certain way.

Assume we have the Person class, which contains some personal data – First Name, Last Name, and Birth date.

Consider the following points:

  1. What is the minimum required number of class modifications to assure comparing class objects by values with the help of the standard .NET architecture?
  2. What is the minimum required number of class modifications to assure comparing class objects by values (every time, if not explicitly stated that objects may be compared by a reference) with the help of the standard .NET architecture?

For each case, we will see the best way to compare objects by value to get a consistent, compact, copy-paste free, and productive code. It is not as trivial as it may seem for the first time.

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Composition and Interfaces in OOP World

In the object-oriented programming world, the concept of inheritance has been criticized for a long time.

There are quite a lot of arguments:

  • A derived class inherits all the parent’s data and behavior that is not always necessary. When modifying a parent class, some data and behavior that are not supposed to be in the derived class get into it;
  • Virtual methods are less productive. If a language allows declaring a non-virtual method, what would you do when you need to override one in an inherited method? You can mark the method with the new keyword, however, in this case, polymorphism will not work. The consequent use of this object may cause unexpected behavior, depending on the type the object is going to be converted to.
  • The vast majority of languages do not allow multiple inheritance.
  • There are tasks where inheritance is helpless. Consider the case, when you need to create a container (array, list, or set) and implement the same behavior for elements with different types. In addition, you need to provide static typing. In this case, generics will come to help.

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