maybe 0.2.3

No more null errors.

maybe

No more null check with an dart equivalent of Maybe (Haskel, Elm) / Option (F#).

Usage

The key is that you need to call the some or when to access your potential value so you are forced to check its status before using it.

Maybe<T>.nothing : creating an optionnal item that is empty

final maybe = Maybe<String>.nothing();

Maybe.some : creating an optionnal item with a value

final maybe = Maybe.some("hello world");

final isNothing = Maybe<String>.some(null); // By default `some` with a null value is converted to `nothing`
final isNotNothing = Maybe<String>.some(null, nullable: true);

some : extracting some value

final maybe = Maybe.some("hello world");
final value = some(maybe, "default"); // == "hello world"

final maybe = Maybe<String>.nothing();
final value = some(maybe, "default"); // == "default"

nothing : testing if some value

final maybe = Maybe.some("hello world");
final value = nothing(maybe); // false

final maybe = Maybe<String>.nothing();
final value = nothing(maybe); // true

when : triggering an action

var maybe = Maybe.some("hello world");
when(maybe, iSome: (v) {
    print(v); // "hello world"
});

// Defining nothing
maybe = Maybe.nothing();
when(maybe, isSome: (v) {
    print(v); // not called!
});

// You can add a default value when nothing
maybe = Maybe<String>.some(null);
when(maybe, isSome: (v) {
        print(v); // "hello world"
    }, 
    defaultValue: () => "hello world");

map : converts a value type to another

var maybe = Maybe.some("hello world");
var converted = map<String,int>(maybe, (v) => v.length);
var value = some(converted,0); // == 11

var maybe = Maybe<String>.nothing();
var converted = map<String,int>(maybe, (v) => v.length);
var value = some(converted, 0); // == 0