How to Correctly Implement Type Assertion for Database Driver Compatibility in Golang?

Golang Type Assertion for Database Driver Compatibility

In this example, a type named Role is defined as a type alias for the string type. The goal is to implement the Valuer and Scanner interfaces to work with a database driver. However, an error is encountered during compilation due to the type conversion in the Scan method.

Specifically, the code attempts to assign the converted string value to the pointer r of type Role. However, the correct way to perform type assertion in this case is by using the assignment syntax r = Role(value.(string))*. This assigns the converted value directly to the dereferenced Role variable.

Additionally, the Value method signature for a driver.Valuer is not as defined in the code. It should be func (r Role) Value() (driver.Value, error). This method returns the string representation of the Role value.

Here is a corrected example of the Scan and Value methods:

func (r *Role) Scan(value interface{}) error {
    *r = Role(value.(string))
    return nil
}

func (r Role) Value() (driver.Value, error) {
    return string(r), nil
}

By making these adjustments, the code will compile successfully and allow the Role type to be used with the database driver.

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