Function Options: return err to handle errors?

guettli · July 12, 2022, 7:37pm

I found this git repo with go patterns:

crazybber/awesome-patterns/blob/master/idiom/functional-options.md

# Functional Options

Functional options are a method of implementing clean/eloquent APIs in Go.
Options implemented as a function set the state of that option.

## Implementation

### Options

```go
package file

type Options struct {
	UID         int
	GID         int
	Flags       int
	Contents    string
	Permissions os.FileMode
}

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For example this, does not allow that evaluating the given argument results in an error:

func UID(userID int) Option {
	return func(args *Options) {
		args.UID = userID
	}
}

Wouldn’t it be better, if Options would be defined like this?

type Option func(*Options) error

christophberger · July 14, 2022, 8:17am

Hi @guettli,

In theory, setting an option should be simple enough to be an error-free operation. If the option needs to be calculated beforehand for some reason, and if this calculation can result in an error, this can be done before calling the option function.