Solving `type mismatch; found : X required: Y` Error in Scala

Understanding the issue

If you are coding in Scala, it’s not uncommon to come across an error message that reads something like this: ‘type mismatch; found : X required: Y’. The error message is Scala’s way of telling you that a value or an expression of type X was found where a value or an expression of type Y was expected.

An Example Scenario of this Error

For instance, consider the following sample code:

var a: String = 12345

Here, Scala expects a value of type String, but it finds a numerical value, 12345, which belongs to type Int. Therefore, the Scala compiler throws the error ‘type mismatch; found : Int required: String’.

Resolving the Error

Understanding the error message is the first step to tackling this problem. The type mismatch error occurs when there is a disconnect between what kind of data Scala is expecting and what it is actually given. Here are a few ways to rectify this issue:

Method 1: Correcting the Data Type

One way to fix it is by making sure that the type of the data you are providing matches with the expected type. In our example, the variable ‘a’ is declared to be a String, but it is given an integer value. Hence, to resolve the error, we shall provide a string value to the variable ‘a’.

var a: String = "12345"

Method 2: Using Type Casting

If you do not have the privilege to change the value, you can cast the type of the data. Going back to our example, you can convert the integer to a string as follows:

var a: String = 12345.toString

Conclusion

In conclusion, the ‘type mismatch’ error in Scala can be easily resolved following one of the two methods mentioned above. Always make sure that the data type of your value or expression aligns with what Scala expects. Happy coding!