Use of Backticks in Kotlin

1. Introduction

Kotlin allows us to surround identifiers with backtick (`) characters when defining variables and functions. In this tutorial, we’ll explore the different ways to utilize backticks and how they can be beneficial.

2. Usage of Backticks

By default, Kotlin adheres to strict naming conventions for functions and variables. However, backticks come to the rescue when we need to name a function or a variable in a way that clashes with these rules.

In this section, let’s look at various uses of backticks in Kotlin code.

2.1. Escaping Keywords

One of the most common uses of backticks is to escape reserved keywords. Normally, we can’t use a keyword as a variable or function name in Kotlin. However, in certain scenarios, we might need to use a keyword as an identifier. In such cases, we can use backticks to escape the keyword. Let’s look at an example:

val `class` = "Hello"

In this case, we needed to define a variable named class, but since it’s a reserved keyword, it isn’t allowed. By using backticks, we can wrap the variable name and escape it.

2.2. Special Characters in an Identifier

Backticks also allow special characters in identifiers, which is particularly useful when interfacing with other languages or systems that use different naming conventions. Normally, a variable name can’t contain special characters like spaces, $, or @. However, by wrapping the variable name in backticks, we can include these characters, providing more clarity or ensuring compatibility. Let’s look at an example:

val `special Name$and@` = "Hello"

Here, we defined a variable with special characters and spaces, which is allowed because we used backticks.

2.3. Test Method Names

Using backticks in Kotlin unit test method names allows for more descriptive and readable test names. This practice enables developers to write test method names that include spaces, special characters, and even entire sentences, making the purpose of each test clearer at a glance. Let’s look at a sample test using the backticks:

@Test
fun `use backticks to escape reserved keywords`() {
    val `class` = "Hello"
    assertEquals("Hello", `class`)
}

From the above code sample, a test method named fun `use backticks to escape reserved keywords`() is more readable than fun shouldEscapeReservedKeywordsWhenBacktickIsUsed(). Better readability improves the maintainability of the test code, making it easier for other developers to understand the intentions and to identify specific tests in test reports. By leveraging backticks, Kotlin developers can create self-documenting tests, thus contributing to better code quality and collaboration.

2.4. Interoperability With Java

Kotlin is fully interoperable with Java, meaning we can call Java code from Kotlin and vice versa. However, sometimes, Java libraries contain methods or fields with names that are reserved keywords in Kotlin. Backticks come in handy to resolve such conflicts, ensuring smooth interoperability.

Let’s define a small class in Java to see this in action:

public class BackTickUsage {
    public boolean is() {
        return true;
    }
}

The BackTickUsage class in Java defines a method is(). However, is is a keyword in Kotlin, so we can’t use it directly:

val backTickUsageJavaClass = BackTickUsage()
backTickUsageJavaClass.is() //Doesn't compile

To refer to the Java method is() in Kotlin, we can use backticks:

backTickUsageJavaClass.`is`()

The code above compiles successfully and invokes the is() method defined in the Java class.

2.5. JSON Parsing and Database Mapping

JSON mapping and database column name mappings are highly relevant scenarios for utilizing backticks in Kotlin. For instance, a third-party API might return JSON content with fields that include reserved keywords or special characters, such as hyphens. In these cases, we can map the JSON fields to the data class properties using backticks, allowing us to use the exact field names provided by the API.

Similarly, when working with database columns that have unconventional names or reserved keywords, backticks enable us to directly map these columns to Kotlin properties without needing to rename them.

Using backticks in these scenarios ensures compatibility and maintains clarity, making it easier to work with external data sources that don’t follow Kotlin’s naming conventions.

3. Pros and Cons of Backticks

Some of the advantages of using backticks include:

• Improves readability of the code
• Avoids naming conflicts
• Improves interoperability
• Descriptive test method names
• Better integration with third-party applications and APIs

However, overuse of backticks can create confusion and hinder readability. As a result, it’s better to use backticks sparingly and only when it provides clear benefits.

4. Conclusion

In this article, we explored various scenarios where backticks can be used in Kotlin code. Backticks offer a powerful and flexible solution for addressing various naming challenges. They allow us to escape reserved keywords, include special characters in variable names, write more descriptive test method names, ensure interoperability with Java, and handle unconventional names in databases and JSON parsing, among other use cases. By leveraging backticks, Kotlin developers can write clearer, more maintainable, and more compatible code.

As always, the sample code used in this article is available over on GitHub.