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March 12, 2021March 19, 2021 A Practical Approach To Object-Oriented

Is A and Has A Concepts in Object-Oriented Design

The ideas of “is a” and “has a” are often discussed as part of object-oriented design. These concepts may seem simple and obvious. However, they can often be confused, and complex systems can blur the lines between them. We start a multi-part episode going over these concepts focused on how “is a” relationships work. Is A and Has A Defined These concepts boil down to simple grammar. For two objects, A and B, here are the options. A is a B if A has all of the traits of B. For example, a poodle is a dog because a poodle has the traits we equate to a dog. A dog is not a poodle, as some dogs have traits that... Read more

March 12, 2021 A Practical Approach To Object-Oriented

Granular Interfaces – How Much OO Is Practical?

The ideas of cohesion and coupling point us to paths that either place functionality in smaller or larger classes. We discuss granular interfaces in this episode as an introduction to those “right-sizing” discussions. Not all OO designs are created equal. Granular Interfaces – Bricks or Sand The best example I have come across in considering how to approach our design’s granularity is comparing sand to bricks. We can construct a building by starting from sand, making blocks of concrete, and then moving on to the structure. However, it is easier when we can start from the blocks or bricks. The Lego Example We can similarly look at the children’s toy Lego bricks. There are various sizes of bricks available. Therefore,... Read more

March 12, 2021March 12, 2021 A Practical Approach To Object-Oriented

Inheritance – Polymorphism In A Hierarchical Manner

We switch gears in this episode and start to look at inheritance. This is a core feature of object-oriented design and the most recognizable attribute. Child classes are utilized through polymorphic support. Thus, we have a natural transition into this popular usage of object-oriented solutions. A Lowest Common Denominator We have discussed the idea of building on methods where possible. When we do, we are creating a lowest common denominator approach to functionality. This is what makes a system logical in its design. Whenever a user (developer) uses a method or attribute there are certain things they can expect that are included. For example, when I have “save” methods in classes, the user expects the class supports persistence. They also... Read more

March 6, 2021 A Practical Approach To Object-Oriented

Interfaces – An Object-Oriented Contract For Usage

This episode, we look at interfaces. These are not supported by all languages. However, when they are supported, they are very useful. The interface specification allows us to provide language-based constraints for our method signatures. It also is an excellent way to enforce consistancy. Interfaces As A Tool For Consistency The most important result of using interfaces is that they enforce a consistent way to communicate with developers. Any class that uses one of these items will be forced to comply with the defined signatures. The language compiler or validations will let the developer know when they are not following the rules. While there might be empty methods allowed, the developer must specifically handle the method and return an empty... Read more

March 4, 2021March 5, 2021 A Practical Approach To Object-Oriented

Flexibility in OOP – Build in hooks for change

One of the essential concepts to understand is flexibility in OOP. A good design requires the ability to extend it. There are ways to do this. However, they require us to incorporate mechanisms for validation and growth. That means we need to find a balance between the core to our functionality and what can be altered as an enhancement. Flexibility in OOP – Many Options There are multiple ways to build flexibility into your object-oriented design. We can use parameters that determine functionality, check for class types, or even plugin commands. These are critical for an effective design as we want to keep our solution flexible enough to grow. Anything rigid is also going to be fragile to some extent. ... Read more

March 4, 2021March 5, 2021 A Practical Approach To Object-Oriented

Code Consistency – Critical For Practical Polymorphism

One of the challenges of good polymorphic design is code consistency. We are building a way to communicate with developers. Therefore, our language or syntax needs to be easy to understand. Likewise, we need to set and meet expectations properly. Code Consistency In Results The most common error I find in this area of coding is found in the values returned. When we stick to native types and numbers, it tends to be easy enough to stay consistent. However, strings and structures lend themselves to issues. For example, an address can have many properties and formats. We may be able to start with an output of: “address line, city, state zip.” However, addresses vary. What happens when we want to... Read more