From 5e6723203013b365c2a60158578f73abf480b8bf Mon Sep 17 00:00:00 2001 From: Jorge Canizales Date: Wed, 9 Mar 2016 13:34:28 -0800 Subject: [PATCH] Make Writeable with single handler robust against stream Writers --- src/objective-c/RxLibrary/GRXWriteable.m | 37 ++++++++++++++++++++---- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/src/objective-c/RxLibrary/GRXWriteable.m b/src/objective-c/RxLibrary/GRXWriteable.m index 2729d62b72f..b122c04ce0c 100644 --- a/src/objective-c/RxLibrary/GRXWriteable.m +++ b/src/objective-c/RxLibrary/GRXWriteable.m @@ -42,11 +42,38 @@ if (!handler) { return [[self alloc] init]; } - return [[self alloc] initWithValueHandler:^(id value) { - handler(value, nil); - } completionHandler:^(NSError *errorOrNil) { - if (errorOrNil) { - handler(nil, errorOrNil); + // We nilify this variable when the block is invoked, so that handler is only invoked once even if + // the writer tries to write multiple values. + __block GRXEventHandler eventHandler = ^(BOOL done, id value, NSError *error) { + // Nillify eventHandler before invoking handler, in case the latter causes the former to be + // executed recursively. Because blocks can be deallocated even during execution, we have to + // first retain handler locally to guarantee it's valid. + // TODO(jcanizales): Just turn this craziness into a simple subclass of GRXWriteable. + GRXSingleHandler singleHandler = handler; + eventHandler = nil; + + if (value) { + singleHandler(value, nil); + } else if (error) { + singleHandler(nil, error); + } else { + NSDictionary *userInfo = @{ + NSLocalizedDescriptionKey: @"The writer finished without producing any value." + }; + // Even though RxLibrary is independent of gRPC, the domain and code here are, for the moment, + // set to the values of kGRPCErrorDomain and GRPCErrorCodeInternal. This way, the error formed + // is the one user of gRPC would expect if the server failed to produce a response. + // + // TODO(jcanizales): Figure out a way to keep errors of RxLibrary generic without making users + // of gRPC take care of two different error domains and error code enums. A possibility is to + // add error handling to GRXWriters or GRXWriteables, and use them to translate errors between + // the two domains. + singleHandler(nil, [NSError errorWithDomain:@"io.grpc" code:13 userInfo:userInfo]); + } + }; + return [self writeableWithEventHandler:^(BOOL done, id value, NSError *error) { + if (eventHandler) { + eventHandler(done, value, error); } }]; }