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Functional error handling in Scala alvin January 10, 2018 - 2:36pm

Because functional programming is like algebra, there are no null values or exceptions. But of course you can still have exceptions when you try to access servers that are down or files that are missing, so what can you do? This lesson demonstrates the techniques of functional error handling in Scala.

How to find regex patterns in Scala strings

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 1.7, “Finding Patterns in Scala Strings.”

Problem

You need to determine whether a Scala String contains a regular expression pattern.

Scala best practice: How to use the Option/Some/None pattern

Table of Contents1 - Problem2 - Solution3 - Returning an Option from a method4 - Getting the value from an Option5 - Using Option with Scala collections6 - Using Option with other frameworks7 - Using Try, Success, and Failure8 - Using Either, Left, and Right9 - Discussion10 - Don’t use the get method with Option11 - See Also12 - The Scala Cookbook

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 20.6, “Scala best practice: How to use the Option/Some/None pattern.”

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Problem

For a variety of reasons, including removing null values from your Scala code, you want to use what I call the Option/Some/None pattern. Or, if you’re interested in a problem (exception) that occurred while processing code, you may want to return Try/Success/Failure from a method instead of Option/Some/None.

Scala: How to declare a variable (var) before using it in try/catch/finally alvin June 7, 2015 - 4:04pm

This is an excerpt from the Scala Cookbook (partially modified for the internet). This is Recipe 3.17, “How to declare a variable (var) before using it in try/catch/finally.”

Problem

You want to use an object in a try block, and need to access it in the finally portion of the block, such as when you need to call a close method on an object.

Scala: How to parse a number from a String alvin May 30, 2015 - 6:34pm

Scala FAQ: How do I parse a number (Int, Long, Float, etc.) from a String in Scala?

Solution

Use the to* methods that are available on a String (courtesy of the Scala StringLike trait):

Scala: Idiomatic processing of an Option alvin October 25, 2014 - 9:12am

This image comes from this article. I don’t like the fold approach at all, but it shows a nice way to use map instead of match/case when processing an Option in Scala.

Scala Option, Some, None syntax examples alvin April 19, 2013 - 8:15am

Today I’m sharing some examples of the Scala Option/Some/None syntax. These examples will show how to use an Option for the var fields in a Scala class. Then I’ll show how to set those Option fields, and then get the values from the Option fields.

To get started, we’ll need a little case class to represent an Address:

How to declare, set, and use Option, Some, and None fields in Scala alvin April 18, 2013 - 9:20am

Again not much time for a discussion today, but if you’re looking for an example of how to declare, set, and use Option fields in Scala, I hope this source code is helpful:

Initialize Scala variables with Option, None, and Some (not null) alvin February 1, 2013 - 10:51am

Summary: How to properly use the Scala Option/Some/None idiom to initialize empty var fields -- and specifically how not to use null values for the same purpose.

When you get started in the Scala world, you quickly learn that null values are a bad thing. Scala makes it easy to replace null values with something better, and that something better is what I call the Option/Some/None pattern (or idiom).