Add Transform::argumentTo

Author: tomphp

README.md

@@ -74,7 +74,7 @@ With code like this:
 $names = array_map(Transform::callMethod('getName'), $allUsers);
 ```
 
-### Transform::callMethod
+### Transform::callMethod($methodName)
 
 ```php
 Transform::classMethod('getName');
@@ -86,8 +86,7 @@ function ($object) {
 }
 ```
 
-
-### Transform::getEntry
+### Transform::getEntry($name)
 
 ```php
 Transform::getEntry('name');
@@ -108,3 +107,22 @@ function ($array) {
     return $array['user']['name'];
 }
 ```
+
+### Transform::argumentTo($callable)
+
+```php
+Transform::getEntry('strtolower');
+
+// Generates:
+
+function ($value) {
+    return strtolower($value);
+}
+```
+
+`$callable` can be any of the following:
+
+* `'functionName'`
+* `function ($value) { /* ... */ }`
+* `[$object, 'methodName']`
+* `['ClassName', 'staticMethodName']`

src/Transform.php

@@ -44,4 +44,20 @@ public static function getEntry($name)
             return $array;
         };
     }
+
+    /**
+     * Returns a transformer calls the given callable with its value as the
+     * argument and returns the result.
+     *
+     * @param string|string[] $name Providing an array will walk multiple levels
+     *                              into the array.
+     *
+     * @return callable
+     */
+    public static function argumentTo($callable)
+    {
+        return function ($value) use ($callable) {
+            return $callable($value);
+        };
+    }
 }

tests/Transform/ArgumentToTest.php

@@ -0,0 +1,63 @@
+<?php
+
+namespace tests\TomPHP\Predicate;
+
+use PHPUnit_Framework_TestCase;
+use TomPHP\Predicate\Transform;
+
+final class ArgumentToTest extends PHPUnit_Framework_TestCase
+{
+    /** @test */
+    public function it_calls_a_function_by_name_with_the_value_as_an_argument_and_returns_the_result()
+    {
+        $fn = Transform::argumentTo('strtolower');
+
+        $this->assertSame('tom', $fn('Tom'));
+    }
+
+    /** @test */
+    public function it_calls_a_function_with_the_value_as_an_argument_and_returns_the_result()
+    {
+        $fn = Transform::argumentTo(function ($value) {
+            return $value + 1;
+        });
+
+        $this->assertSame(5, $fn(4));
+    }
+
+    /** @test */
+    public function it_calls_an_object_method_with_the_value_as_an_argument_and_returns_the_result()
+    {
+        $fn = Transform::argumentTo([$this, 'decrement']);
+
+        $this->assertSame(3, $fn(4));
+    }
+
+    /** @test */
+    public function it_calls_a_static_method_with_the_value_as_an_argument_and_returns_the_result()
+    {
+        $fn = Transform::argumentTo([__CLASS__, 'staticDecrement']);
+
+        $this->assertSame(3, $fn(4));
+    }
+
+    /**
+     * @param int $value
+     *
+     * @return int
+     */
+    public function decrement($value)
+    {
+        return $value - 1;
+    }
+
+    /**
+     * @param int $value
+     *
+     * @return int
+     */
+    public static function staticDecrement($value)
+    {
+        return $value - 1;
+    }
+}