Explain the use of Go's blank identifiers for discarding values?

Table of content

• Introduction
• What Are Blank Identifiers in Go?
  • Characteristics of Blank Identifiers:
• How to Use Blank Identifiers in Go?
  •  Ignoring Unused Return Values from Functions
  •  Ignoring Values in Loops
  •  Ignoring Return Values from Type Assertions
• Practical Examples
  • Example 1: Discarding Return Values from a Function
  • Example 2: Ignoring Channels Values in Go Concurrency
• Benefits of Using Blank Identifiers in Go
• Conclusion

Introduction

In Go, a blank identifier (represented by an underscore _) is used to discard values that you don't need. It serves as a placeholder for values that are returned from functions or operations but are not required for further use. Blank identifiers help keep your Go code clean and concise by allowing you to ignore unneeded return values without causing compiler errors.

What Are Blank Identifiers in Go?

A blank identifier is a special identifier represented by an underscore (_). It is used when you want to ignore or discard a value, particularly in multiple return value functions or when you don't want to handle all the return values provided by an operation. The blank identifier acts as a write-only variable, meaning you can assign to it, but you cannot read from it.

Characteristics of Blank Identifiers:

1. Ignored by the Compiler: Blank identifiers are treated as if the values assigned to them do not exist.
2. No Memory Allocation: The use of a blank identifier does not allocate memory or affect performance.
3. Used in Declarations: They are often used in variable declarations, function calls, and type assertions to ignore specific return values.

How to Use Blank Identifiers in Go?

Blank identifiers are used in various scenarios where values need to be discarded or ignored. Here are some common use cases:

 Ignoring Unused Return Values from Functions

Go functions can return multiple values, and sometimes you might not need all of them. The blank identifier allows you to ignore those unneeded values.

Explanation:

• The divide function returns two values: the result of the division and an error.
• Since we are not interested in the error value in this case, we use a blank identifier (_) to ignore it.

 Ignoring Values in Loops

Blank identifiers can be used in loops where only some parts of the range values are needed, such as ignoring the index or value in a range loop.

Explanation:

• In the range loop, the blank identifier (_) is used to ignore the index returned by the loop, as only the values are needed.

 Ignoring Return Values from Type Assertions

Type assertions in Go can return two values: the asserted value and a boolean indicating whether the assertion was successful. If you only need the asserted value, you can use a blank identifier to ignore the boolean.

Explanation:

• The type assertion i.(string) returns the value str and a boolean indicating success or failure.
• The blank identifier (_) is used to discard the boolean value.

Practical Examples

Example 1: Discarding Return Values from a Function

You may encounter a function that returns a result and an error, but you are only interested in the result.

Explanation:

• The fetchData function returns three values, but only the first (id) is needed. The blank identifiers (_) are used to discard the unwanted values.

Example 2: Ignoring Channels Values in Go Concurrency

When working with Go channels, you might receive values that are not needed. Blank identifiers can help discard those values.

Explanation:

• The <-timer.C expression receives the value sent from the channel, but the value itself is not used. The blank identifier (_) is implicitly used to discard the channel's value.

Benefits of Using Blank Identifiers in Go

1. Cleaner Code: Helps keep the code clean by avoiding unused variable declarations.
2. Prevents Compiler Errors: The Go compiler throws errors for unused variables; blank identifiers prevent these errors.
3. Improves Code Readability: Makes the code more readable by explicitly indicating which values are irrelevant.

Conclusion

Go's blank identifiers are a powerful tool for discarding unwanted values, enhancing code readability, and preventing compiler errors. They are particularly useful in scenarios where functions return multiple values, but not all values are needed. By understanding when and how to use blank identifiers, you can write cleaner, more efficient Go code.