go-optional 
A library that provides Go Generics friendly "optional" features.
Synopsis
true fmt.Printf("%v\n", some.IsNone()) // => false v, err := some.Take() fmt.Printf("err is nil: %v\n", err == nil) // => err is nil: true fmt.Printf("%d\n", v) // => 123 mapped := optional.Map(some, func (v int) int { return v * 2 }) fmt.Printf("%v\n", mapped.IsSome()) // => true mappedValue, _ := some.Take() fmt.Printf("%d\n", mappedValue) // => 246 ">
some := optional.Some[int](123) fmt.Printf("%v\n", some.IsSome()) // => true fmt.Printf("%v\n", some.IsNone()) // => false v, err := some.Take() fmt.Printf("err is nil: %v\n", err == nil) // => err is nil: true fmt.Printf("%d\n", v) // => 123 mapped := optional.Map(some, func (v int) int { return v * 2 }) fmt.Printf("%v\n", mapped.IsSome()) // => true mappedValue, _ := some.Take() fmt.Printf("%d\n", mappedValue) // => 246
false fmt.Printf("%v\n", none.IsNone()) // => true _, err := none.Take() fmt.Printf("err is nil: %v\n", err == nil) // => err is nil: false // the error must be `ErrNoneValueTaken` mapped := optional.Map(none, func (v int) int { return v * 2 }) fmt.Printf("%v\n", mapped.IsNone()) // => true ">
none := optional.None[int]() fmt.Printf("%v\n", none.IsSome()) // => false fmt.Printf("%v\n", none.IsNone()) // => true _, err := none.Take() fmt.Printf("err is nil: %v\n", err == nil) // => err is nil: false // the error must be `ErrNoneValueTaken` mapped := optional.Map(none, func (v int) int { return v * 2 }) fmt.Printf("%v\n", mapped.IsNone()) // => true
and more detailed examples are here.
Docs
Tips
- it would be better to deal with an Option value as a non-pointer because if the Option value can accept nil it becomes worthless
Current Status
Currently (at the moment: Nov 18, 2021), go 1.18 has not been released yet, so if you'd like to try this, please use the tip runtime.
Of course, the new runtime version hasn't been released yet so this library has the possibility to change the implementation as well.
Known Issues
The runtime raises a compile error like "methods cannot have type parameters", so Map(), MapOr(), Zip() and ZipWith() has been providing as functions. Basically, it would be better to provide them as the methods, but currently, it compromises with the limitation.
Author
moznion ([email protected])
