Adding ability to cache promises.

2 files changed, 96 insertions, 20 deletions

diff --git a/gwtquery-core/src/main/java/com/google/gwt/query/client/plugins/deferred/FunctionDeferred.java b/gwtquery-core/src/main/java/com/google/gwt/query/client/plugins/deferred/FunctionDeferred.java
index 3b40fdce..771749f8 100644
--- a/gwtquery-core/src/main/java/com/google/gwt/query/client/plugins/deferred/FunctionDeferred.java
+++ b/gwtquery-core/src/main/java/com/google/gwt/query/client/plugins/deferred/FunctionDeferred.java
@@ -21,29 +21,36 @@ import com.google.gwt.query.client.Promise.Deferred;
  * execution in pipelined processes.
  * 
  * They have access to the associated deferred object via a method which
- * will be called only in the case the previous promise is resolved
+ * will be called only in the case the previous promise is resolved.
+ *
+ * We can reuse the function and it will create new promises or will return
+ * the last one depending on the value of cache. It is very useful for caching
+ * server calls which we just want execute once like login, etc.
  *
  * <pre>
- *    Promise doSomething = new PromiseFunction() {
+ *    Function login = new FunctionDeferred() {
  *      @Override
  *      public void f(Deferred dfd) {
- *        dfd.notify("hi");
- *        dfd.resolve("done");
+ *        dfd.resolve("logged in as james-bond at " + new Date());
  *      }
- *    };
- *    
- *    doSomething.then(new FunctionDeferred() {
- *      public void f(Deferred dfd) {
- *        dfd.resolve("deferred " + arguments(0));
+ *    }.withCache(RESOLVED);
+ *
+ *    when(login)
+ *    .then(new Function() {
+ *      public void f() {
+ *        String loginMessage = arguments(0);
  *      }
  *    });
  * </pre>
  */
 public abstract class FunctionDeferred extends Function {
-  
+
+  public static enum CacheType {NONE, ALL, RESOLVED, REJECTED};
+
   protected Deferred dfd;
   public Function resolve, reject;
-  
+  private CacheType cache = CacheType.NONE;
+
   /**
    * This function is called once the the previous promise in the
    * pipe is resolved, and the new created deferred is available.
@@ -51,20 +58,46 @@ public abstract class FunctionDeferred extends Function {
    * You have to override it, and resolve the new promise
    */
   protected abstract void f(Deferred dfd);
-  
+
   /**
    * This function is called when the previous promise in the pipe
    * is resolved. 
    */
   public final Object f(Object... args) {
-    return new PromiseFunction() {
-      public void f(Deferred dfd) {
-        FunctionDeferred.this.resolve = resolve;
-        FunctionDeferred.this.reject = reject;
-        FunctionDeferred.this.dfd = dfd;
-        FunctionDeferred.this.f(dfd);
-      }
-    };
+    return  dfd != null &&
+        (cache == CacheType.ALL ||
+         cache == CacheType.RESOLVED && dfd.promise().isResolved() ||
+         cache == CacheType.REJECTED && dfd.promise().isRejected())
+        ? dfd.promise()
+        : new PromiseFunction() {
+          public void f(Deferred dfd) {
+            FunctionDeferred.this.resolve = resolve;
+            FunctionDeferred.this.reject = reject;
+            FunctionDeferred.this.dfd = dfd;
+            FunctionDeferred.this.f(dfd);
+          }
+       };
   }
 
+  /**
+   * Configure whether cache the promise the first time it is resolved
+   * or create new promises each time the function is executed.
+   *
+   * By default cache is disabled.
+   */
+  public FunctionDeferred withCache(CacheType type) {
+    cache = type;
+    return this;
+  }
+  
+  /**
+   * Reset the cache so as a new invocation to this function will
+   * execute it instead of restoring old values from cache.
+   */
+  public FunctionDeferred resetCache() {
+    if (dfd != null && !dfd.promise().isPending()) {
+      dfd = null;
+    }
+    return this;
+  }
 }
diff --git a/gwtquery-core/src/test/java/com/google/gwt/query/client/deferred/DeferredTest.java b/gwtquery-core/src/test/java/com/google/gwt/query/client/deferred/DeferredTest.java
index 45eb6064..9c7f16ef 100644
--- a/gwtquery-core/src/test/java/com/google/gwt/query/client/deferred/DeferredTest.java
+++ b/gwtquery-core/src/test/java/com/google/gwt/query/client/deferred/DeferredTest.java
@@ -24,6 +24,7 @@ import com.google.gwt.query.client.GQuery;
 import com.google.gwt.query.client.Promise.Deferred;
 import com.google.gwt.query.client.plugins.deferred.Callbacks;
 import com.google.gwt.query.client.plugins.deferred.Callbacks.Callback;
+import com.google.gwt.query.client.plugins.deferred.FunctionDeferred.CacheType;
 import com.google.gwt.query.client.plugins.deferred.FunctionDeferred;
 import com.google.gwt.query.client.plugins.deferred.PromiseFunction;
 
@@ -371,4 +372,46 @@ public class DeferredTest extends GWTTestCase {
     });
   }
 
+  private Boolean deferredData;
+
+  public void testFunctionDeferredCache() {
+
+    FunctionDeferred cachedFunction = new FunctionDeferred() {protected void f(Deferred dfd) {
+        dfd.resolve(deferredData);
+    }};
+
+    Function setDeferredDataToTrue = new Function(){public void f() {
+      deferredData = true;
+    }};
+
+    Function setDeferredDataToFalse = new Function(){public void f() {
+      deferredData = false;
+    }};
+
+    Function assertDeferredDataIsFalse = new Function(){public void f() {
+      Boolean data = arguments(0);
+      assertFalse(data);
+    }};
+
+    Function assertDeferredDataIsTrue = new Function(){public void f() {
+      Boolean data = arguments(0);
+      assertTrue(data);
+    }};
+
+    when(setDeferredDataToTrue, cachedFunction.withCache(CacheType.ALL))
+      .always(setDeferredDataToFalse)
+      .done(assertDeferredDataIsTrue)
+      .then(cachedFunction)
+      .done(assertDeferredDataIsTrue)
+      .then(cachedFunction.withCache(CacheType.REJECTED))
+      .done(assertDeferredDataIsFalse)
+      .always(setDeferredDataToTrue)
+      .then(cachedFunction.withCache(CacheType.RESOLVED))
+      .done(assertDeferredDataIsFalse)
+      .then(cachedFunction.resetCache())
+      .done(assertDeferredDataIsTrue)
+      .then(cachedFunction)
+      .done(assertDeferredDataIsTrue)
+    ;
+  }
 }