Return Promise for set and remove

README.md

@@ -47,7 +47,8 @@ This example fetches the value of the key `foo` and passes it to the
 `var_dump` function. You can use any of the composition provided by
 [promises](https://github.com/reactphp/promise).
 
-If the key `foo` does not exist, the promise will be fulfilled with `null` as value.
+If the key `foo` does not exist, the promise will be fulfilled with `null` as value. On 
+any error it will also resolve with `null`.
 
 #### set()
 
@@ -56,8 +57,9 @@ $cache->set('foo', 'bar');
 ```
 
 This example eventually sets the value of the key `foo` to `bar`. If it
-already exists, it is overridden. No guarantees are made as to when the cache
-value is set. If the cache implementation has to go over the network to store
+already exists, it is overridden. To provide guarantees as to when the cache
+value is set a promise is returned. The promise will fulfill with `true` on success 
+or `false` on error. If the cache implementation has to go over the network to store 
 it, it may take a while.
 
 #### remove()
@@ -67,7 +69,8 @@ $cache->remove('foo');
 ```
 
 This example eventually removes the key `foo` from the cache. As with `set`,
-this may not happen instantly.
+this may not happen instantly and a promise is returned to provide guarantees whether 
+or not the item has been removed from cache.
 
 ### ArrayCache
 

src/ArrayCache.php

@@ -11,7 +11,7 @@ class ArrayCache implements CacheInterface
  public function get($key)
 {
  if (!isset($this->data[$key])){
- return Promise\resolve(null);
+ return Promise\resolve();
  }
 
  return Promise\resolve($this->data[$key]);
@@ -20,10 +20,12 @@ public function get($key)
  public function set($key, $value)
 {
  $this->data[$key] = $value;
+ return Promise\resolve(true);
  }
 
  public function remove($key)
 {
  unset($this->data[$key]);
+ return Promise\resolve(true);
  }
 }

src/CacheInterface.php

@@ -8,27 +8,30 @@ interface CacheInterface
 {
  /**
  * Retrieve an item from the cache, resolves with its value on
- * success or null when no item can be found.
+ * success or null when no item can be found or when an error occurs.
  *
  * @param string $key
  * @return PromiseInterface
  */
  public function get($key);
 
  /**
- * Store an item in the cache.
+ * Store an item in the cache, returns a promise which resolves to true on success or
+ * false on error.
  *
  * @param string $key
  * @param mixed $value
- * @return void
+ * @return PromiseInterface Returns a promise which resolves to true on success of false on error
  */
  public function set($key, $value);
 
  /**
- * Remove an item from the cache.
+ * Remove an item from the cache, returns a promise which resolves to true on success or
+ * false on error. When the $key isn't found in the cache it also
+ * resolves true.
  *
  * @param string $key
- * @return void
+ * @return PromiseInterface Returns a promise which resolves to true on success of false on error
  */
  public function remove($key);
 }

tests/ArrayCacheTest.php

@@ -6,6 +6,9 @@
 
 class ArrayCacheTest extends TestCase
 {
+ /**
+ * @var ArrayCache
+ */
  private $cache;
 
  public function setUp()
@@ -33,9 +36,17 @@ public function getShouldResolvePromiseWithNullForNonExistentKey()
  /** @test */
  public function setShouldSetKey()
 {
- $this->cache
+ $setPromise = $this->cache
  ->set('foo', 'bar');
 
+ $mock = $this->createCallableMock();
+ $mock
+ ->expects($this->once())
+ ->method('__invoke')
+ ->with($this->identicalTo(true));
+
+ $setPromise->then($mock);
+
  $success = $this->createCallableMock();
  $success
  ->expects($this->once())
@@ -53,9 +64,17 @@ public function removeShouldRemoveKey()
  $this->cache
  ->set('foo', 'bar');
 
- $this->cache
+ $removePromise = $this->cache
  ->remove('foo');
 
+ $mock = $this->createCallableMock();
+ $mock
+ ->expects($this->once())
+ ->method('__invoke')
+ ->with($this->identicalTo(true));
+
+ $removePromise->then($mock);
+
  $this->cache
  ->get('foo')
  ->then(