This document discusses fluent interfaces and proposes a pipe operator to improve them. It notes that fluent interfaces can be difficult to extend and combine multiple interfaces. It then demonstrates how to "unwrap" objects in a fluent chain to allow operations like logging. Finally, it proposes a pipe operator inspired by functional programming to improve readability and composability of fluent code by reversing the order of operations.

1. ČTVRTKON
FLUENT INTERFACES

2. PROBLÉM SKLÁDÁNÍ FUNKCÍ A OBJEKTŮ - POSTFIX NOTACE
$json = new ParseJson(
new AssertResponseStatus(
new RequestWithHeader(
new AuthHeader('basic', $username, $password),
new RequestWithMethod(
'GET',
new Request('example.com')
)
),
200
)
).toString();

3. TEXT
FLUENT INTEFACE
class Request {
// ...
function withMethod($method) {
$this->method = $method;
return $this;
}
// ...
}

4. TEXT
FLUENT INTEFACE
$json = new Request('example.com')
->withMethod('GET')
->withHeader(new AuthHeader('basic', $username, $password))
->assertResponseStatus(200)
->parseJson()
->toString();

5. THE API IS PRIMARILY DESIGNED TO BE
READABLE AND TO FLOW. THE PRICE OF THIS
FLUENCY IS MORE EFFORT, BOTH IN THINKING
AND IN THE API CONSTRUCTION ITSELF.
Martin Fowler
TEXT

6. TEXT
NEVÝHODY FLUENT INTERFACE
‣Špatná rozšiřitelnost
‣Nemožnost spojit do "fluentu" více rozhraní
‣Proxy / dekorátory a "unwrapnutí" $this!

7. TEXT
UNWRAP
class FluentCounter {
$i = 0;
function inc() {
$this->i++;
return $this;
}
}
class LoggerCounter {
$this->counter = new FluentCounter();
function inc() {
echo "calling incn";
return $this->counter->inc();
}
}
new LoggerCounter(new FluentCounter())->inc()->inc()->inc(); // "calling inc" (jednou)

8. TEXT
UNWRAP
class FluentCounter {
$i = 0;
function inc() {
$this->i++;
return $this;
}
}
class LoggerCounter {
$this->counter = new FluentCounter();
function inc() {
echo "calling incn";
$this->counter = $this->counter->inc();
return $this;
}
}
new LoggerCounter(new FluentCounter())->inc()->inc()->inc(); // "calling inc" (třikrát)

9. TEXT
NEŠLO BY PROSTĚ OTOČIT POŘADÍ?
function revert2($fn1, $fn2) {
return function (...$args) use ($fn1, $fn2) {
return $fn2($fn1(...$args));
};
}
function fn1($x) {
return 'fn1(' . $x . ')';
}
function fn2($x) {
return 'fn2(' . $x . ')';
}
echo revert2('fn1', 'fn2')('x'); // 'fn2(fn1(x))'

10. TEXT
JAK TO UDĚLAT PRO N FUNKCÍ?

11. TEXT
JAK TO UDĚLAT PRO N FUNKCÍ?
function revert2($fn1, $fn2) {
return function (...$args) use ($fn1, $fn2) {
return $fn2($fn1(...$args));
};
}
function revert($f1, ...$fns) {
return array_reduce($fns, 'revert2', $f1);
}
// final version:
function revert($f1, ...$fns) {
return array_reduce($fns, function ($fn1, $fn2) {
return function (...$args) use ($fn1, $fn2) { return $fn2($fn1(...$args)); };
}, $f1);
}

12. REVERT = PIPE OPERÁTOR

13. TEXT
POUŽITÍ
$json = pipe(
new Request('example.com'),
new WithMethod('GET'),
new WithHeader(new AuthHeader('basic', $username, $password),
new AssertResponseStatus(200),
new ParseJson(),
)->toString();
// s pipe operátorem:
$json = new Request('example.com')
|> new WithMethod($$, 'GET'),
|> new WithHeader(new AuthHeader('basic', $username, $password), $$),
|> new AssertResponseStatus($$, 200),
|> new ParseJson(),
|> toString();

14. TEXT
PIPE OPERÁTOR V OSTATNÍCH JAZYCÍCH
▸ PHP: https://wiki.php.net/rfc/pipe-operator
▸ javascript: https://github.com/tc39/proposal-pipeline-
operator
▸ C#: https://github.com/dotnet/csharplang/issues/96
▸ ...

15. DÍKY ZA POZORNOST