Chaining

_.m supports method chaining for a fluent API style.

OO-Wrapper: __()

Wraps an object to enable chaining. Call value() to unwrap.

A* lyrics = AA(@[@"I'm", @"a", @"little", @"teapot"]);
S* song = __(lyrics)
    .map(^id(S* word, ...) { return [word uppercaseString]; })
    .reduce(^id(S* memo, S* word, ...) {
        return [memo stringByAppendingFormat:@" %@", word];
    }, @"")
    .value();
// => " I'M A LITTLE TEAPOT"

chain

Starts a chain. All future method calls return wrapped objects.

A* stooges = AA(@[
    OKV({@"name", @"curly"}, {@"age", N.I(25)}),
    OKV({@"name", @"moe"}, {@"age", N.I(21)}),
    OKV({@"name", @"larry"}, {@"age", N.I(23)})
]);

S* youngest = _.chain(stooges)
    .sortBy(^id(O* stooge, ...) { return stooge[@"age"]; })
    .map(^id(O* stooge, ...) {
        return [NSString stringWithFormat:@"%@ is %@",
                stooge[@"name"], stooge[@"age"]];
    })
    .first()
    .value();
// => "moe is 21"

value

Extracts the value of a wrapped object.

A* result = __(AI(1, 2, 3)).value();
// => [1, 2, 3]

Chaining Example

// Without chaining
A* filtered = _.filter(list, predicate);
A* mapped = _.map(filtered, transform);
A* sorted = _.sortBy(mapped, comparator);
id first = _.first(sorted);

// With chaining - much cleaner!
id result = _.chain(list)
    .filter(predicate)
    .map(transform)
    .sortBy(comparator)
    .first()
    .value();