Breaking and Mending Compatibility

Michael Feathers
February 22, 2018

We often think that backward compatibility is hard, but actually it’s rather easy. Any project with users has a built-in mechanism for maintaining backward compatibility — people complain when it’s broken. That’s how you know. And, most of the time they let you know quickly.

The problem with this is that users can force unwanted . . .

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Negative Architecture

Guiding software by flipping figure and ground

Michael Feathers
January 02, 2018

Silvrback blog image

You’ve probably seen this picture before. It’s one of several images that people use to show how perception works. You either see a vase or two faces looking at each other. In the terminology of Gestalt Psychology, one becomes the figure and the other becomes the ground. We can switch between the vase and the faces but we can’t see . . .

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10 Papers Every Developer Should Read

(At Least Twice)

Michael Feathers
November 15, 2017

(This is a requested repost of a lost blog I wrote in 2009. I'd change a few things, but not many)

I spent most of yesterday afternoon working on a paper I’m co-writing. It was one of those days when the writing came easy. I was moving from topic to topic, but then I realized that I was reaching too far backward – I was . . .

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Knowing What Is There

Michael Feathers
October 20, 2017

If you want to know about the mechanics of refactoring there are quite a few resources out there. You can even find resources that outline refactoring strategy. But what about mindset? Is there a refactoring mindset that people should be aware of? I think that there is.

A while ago I was working with a team. We had time to refactor . . .

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Converting Queries to Commands

A `Slice and Dice' Refactoring

Michael Feathers
July 11, 2017

When methods focus on a single responsibility, they fall into two broad categories. They are either queries that compute and return some value without producing side effects, or they are commands that change the state of the world or the state of the object they are on.

The former style is more common in functional programming. In . . .

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Edges in Software

Using Edge Cases as Focal Points for Design Choices

Michael Feathers
May 03, 2017

One of my favorite sayings is “If you take care of the corners, the room takes care of itself.”

For the longest while I thought it was something that Frank Lloyd Wright had said but I haven’t been able to find an attribution. Regardless, I think that the idea is sound. The edge cases in our software define it. Ideally, we shouldn’t . . .

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Revealing Interfaces

Making Usage Patterns Explicit in Code

Michael Feathers
January 31, 2017

In nearly every OO application there’s at least one large class. By large, I mean a class that has 15 or more methods. We expect classes to have focus and it’s hard to make the case that a class with that many methods is about one thing. There will be some sort of grouping. Sometimes it’s explicit in the names of the methods, sometimes it’s . . .

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