The Bowling Kata Anti-IF Challenge

"Have you ever noticed how many IFs have been used in Bob Martin's Bowling Kata solution? Is this an effective solution from an evolutionary design perspective?"

In this Workshop, Francesco Cirillo will develop the Bowling Kata in an evolutionary way and without applying the "IF Strategy."

Here you can find the next session of this workshop:

About this Challenge

Francesco's Software Development Challenges are journeys in which Francesco, you and the other participants will develop one or more features of a real application. Francesco will lead the development of the feature to be created and show you how he makes software design decisions, how he applies principles and tools, why he chooses one pattern over another and why he prefers certain practices in specific contexts.

The Story Behind this Challenge

Francesco Cirillo tells the story behind the Bowling Kata Anti-If Challenge.

"This Challenge was born out of a request from Damir, one of the participants in the Software Production You and Me Mentoring Programme. One day, he asked me: 'I would like to see how you would develop the Bowling Kata without IFs.'

I admit that I did not know of the Bowling Kata. This Kata is about developing an application that can calculate the score of a bowling match. Robert Martin provided a solution in 2005 to demonstrate how he applies TDD. Robert Martin's solution is considered by many as a 'procedural solution.' The result of applying the 'IF Strategy' several times to deal with new tests. I understand the reason for my client's request.

	public int score() {
		int score = 0;
		int frameIndex = 0;
		for (int frame = 0; frame < 10; frame++) {
			int frameIndex = 0;
IF=>		if (isStrike(frameIndex)) {
			score += 10 + strikeBonus(frameIndex);
			frameIndex++;
IF=>		} else if (isSpare(frameIndex)) {
      				score += 10 + spareBonus(frameIndex);
					frameIndex += 2;
IF=>		} else {
					score += sumOfBallsInFrame(frameIndex);
					frameIndex += 2;
      		}
      	}
      	return score;
      }
      

	public int score() {
		int score = 0;
        int currentRoll = 0;
        int numFrames = isMartian() ? 12 : (isVenusian() ? 11: 10);
		for (int frame = 0; frame < numFrames; frame++) {
IF=>		if (callistoVariant() && isLastFrame(frame) {
        		while(isStrike(currentRoll, frame)) {
                	score += 10 + sumOfTwoRolls(currentRolls+1);
                    currentRoll++;
                }
IF=>		} else {
IF=>            if(isStrike(currentRoll)) {
                	score += 10 + sumOfTwoRolls(currentRolls + 1);
                    currentRoll++;
                }
            }
IF=>		} if (isSpare(currentRoll)) {
      			score += 10 + rolls[currentRolls+1];
				currentRoll += 2;
IF=>		} else if (isMartian() {
				score += sumOfThreeRolls(currentRolls);
				currentRoll += 3;
IF=>		} else {
				score = sumOfTwoRolls(currentRolls);
				currentRoll += 2;
			}
		}
      	return score;
      }
      
	public boolean isStrike(int currentRoll, int frame) {
IF=>	if (isVenusian()) {
			return rolls[currentRoll] == frame;
		}
		return rolls[currentRoll] == 10;
	}

Objectives

What are the objectives of this Challenge?

1. To solve the Bowling Kata:
   • Develop the initial requirements presented by Bob Martin.
   • Develop the requests proposed by Matteo Vaccari.
   • Develop some other requirements that we can't even imagine right now.
2. To apply an evolutionary and adaptive design process:
   • In particular, since the first time this Kata was done in a TDD way, we will use TDD.
3. Obviously we will not apply the "IF Strategy" to deal with change, complexity and growth.

As a result of this workshop, you will learn to:

Structure

This workshop is organized in four sessions.

Price & Conditions

The price includes:

• Attendance to the live streamed 4-session workshop.
• Access to the pre-recorded workshop (available for a limited time).
• Completed source code for the Kata.

Discounts for groups of four or more are possible. Please contact us for more details.

Choose Your Workshop

Here you can find the next session of this workshop:

Can't make it on any of our dates? We can discuss other options with you. Please contact us for more details.

About the Trainer

Francesco Cirillo

Francesco Cirillo has worked at the forefront of the software industry for more than 30 years. In a career spanning startups, corporations and freelance consulting, he has mentored thousands of professionals, developers, managers and software teams.

Francesco is one of the pioneers of Agile Methods. He started working on XP and TDD in 1999. He was chosen by Kent Beck to develop the XP community in Europe and as reviewer of the second edition of the book Extreme Programming Explained.

Francesco invented the Pomodoro® Technique, a renowned time-management method used by millions of people all over the world, while being a university student looking for a way to get more done in less time.

Read the Francesco Cirillo's complete profile.

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