3 files changed, 141 insertions, 1 deletions
diff --git a/src/objective-c/RxLibrary/GRXImmediateSingleWriter.h b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.h
new file mode 100644
index 0000000000..0ec788f756
--- /dev/null
+++ b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.h
@@ -0,0 +1,50 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "GRXImmediateWriter.h"
+
+/**
+ * Utility to construct GRXWriter instances from values that are immediately available when
+ * required.
+ */
+@interface GRXImmediateSingleWriter : GRXImmediateWriter
+
+/**
+ * Returns a writer that sends the passed value to its writeable and then finishes (releasing the
+ * value).
+ */
++ (GRXWriter *)writerWithValue:(id)value;
+
+@end
diff --git a/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m
new file mode 100644
index 0000000000..0096c996d4
--- /dev/null
+++ b/src/objective-c/RxLibrary/GRXImmediateSingleWriter.m
@@ -0,0 +1,89 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#import "GRXImmediateSingleWriter.h"
+
+@implementation GRXImmediateSingleWriter {
+  id _value;
+  id<GRXWriteable> _writeable;
+}
+
+@synthesize state = _state;
+
+- (instancetype)initWithValue:(id)value {
+  if (self = [super init]) {
+    _value = value;
+    _state = GRXWriterStateNotStarted;
+  }
+  return self;
+}
+
++ (GRXWriter *)writerWithValue:(id)value {
+  return [[self alloc] initWithValue:value];
+}
+
+- (void)startWithWriteable:(id<GRXWriteable>)writeable {
+  _state = GRXWriterStateStarted;
+  _writeable = writeable;
+  [writeable writeValue:_value];
+  [self finish];
+}
+
+- (void)finish {
+  _state = GRXWriterStateFinished;
+  _value = nil;
+  id<GRXWriteable> writeable = _writeable;
+  _writeable = nil;
+  [writeable writesFinishedWithError:nil];
+}
+
+// Overwrite the setter to disallow manual state transition. The getter
+// of _state is synthesized.
+- (void)setState:(GRXWriterState)newState {
+  // Manual state transition is not allowed
+  return;
+}
+
+// Overrides [requestWriter(Transformations):map:] for Protocol Buffers
+// encoding.
+// We need the return value of this map to be a GRXImmediateSingleWriter but
+// the original \a map function returns a new Writer of another type. So we
+// need to override this function here.
+- (GRXWriter *)map:(id (^)(id))map {
+  // Since _value is available when creating the object, we can simply
+  // apply the map and store the output.
+  _value = map(_value);
+  return self;
+}
+
+@end
diff --git a/src/objective-c/RxLibrary/GRXWriter+Immediate.m b/src/objective-c/RxLibrary/GRXWriter+Immediate.m
index 1d55eb3529..ea6e681406 100644
--- a/src/objective-c/RxLibrary/GRXWriter+Immediate.m
+++ b/src/objective-c/RxLibrary/GRXWriter+Immediate.m
@@ -34,6 +34,7 @@
 #import "GRXWriter+Immediate.h"
 
 #import "GRXImmediateWriter.h"
+#import "GRXImmediateSingleWriter.h"
 
 @implementation GRXWriter (Immediate)
 
@@ -50,7 +51,7 @@
 }
 
 + (instancetype)writerWithValue:(id)value {
-  return [GRXImmediateWriter writerWithValue:value];
+  return [GRXImmediateSingleWriter writerWithValue:value];
 }
 
 + (instancetype)writerWithError:(NSError *)error {