How to Type Assert Slices of Interface Values in Go?

Type Asserting Slices of Interface Values

When attempting to type assert a slice of interface values, you may encounter an error similar to:

invalid type assertion: args.([]Symbol) (non-interface type []Node on left)

This error occurs because slices are distinct, non-interface types. To understand why, let's examine the nature of interfaces in Go.

Interfaces are types that define a set of methods that a value must implement. When you create a variable of an interface type, its dynamic type is not fixed, allowing it to hold values of any type that implements the interface.

However, a slice is a collection of values of a specific type, which is固定 of one type. It does not have any methods, making it a non-interface type. Therefore, it makes no sense to assume that a slice of interface values is also an interface.

The Solution

To resolve this error, you can explicitly convert the values in the slice to the desired type, as in the following code:

symbols := make([]Symbol, len(args))
for i, arg := range args { symbols[i] = arg.(Symbol) }

This code creates a new slice of the desired type and iterates through the original slice, converting each value to the desired type. This allows you to use the type-asserted values in your code without encountering the type assertion error.

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