[](https://cocoapods.org/pods/gRPC)
# gRPC for Objective-C
- [Write your API declaration in proto format](#write-protos)
- [Integrate a proto library in your project](#cocoapods)
- [Use the generated library in your code](#use)
- [Use gRPC without Protobuf](#no-proto)
- [Alternatives to the steps above](#alternatives)
- [Install protoc with the gRPC plugin](#install)
- [Install protoc and the gRPC plugin without using Homebrew](#no-homebrew)
- [Integrate the generated gRPC library without using Cocoapods](#no-cocoapods)
While gRPC doesn't require the use of an IDL to describe the API of services, using one simplifies
usage and adds some interoperability guarantees. Here we use [Protocol Buffers][], and provide a
plugin for the Protobuf Compiler (_protoc_) to generate client libraries to communicate with gRPC
services.
## Write your API declaration in proto format
For this you can consult the [Protocol Buffers][]' official documentation, or learn from a quick
example [here](https://github.com/grpc/grpc/tree/master/examples#defining-a-service).
## Integrate a proto library in your project
Install [Cocoapods](https://cocoapods.org/#install).
You need to create a Podspec file for your proto library. You may simply copy the following example
to the directory where your `.proto` files are located, updating the name, version and license as
necessary. You also need to set the `pods_root` variable to the correct value, depending on where
you place this podspec relative to your Podfile.
```ruby
Pod::Spec.new do |s|
s.name = ''
s.version = '0.0.1'
s.license = '...'
s.authors = { '' => '' }
s.homepage = '...'
s.summary = '...'
s.source = { :git => 'https://github.com/...' }
s.ios.deployment_target = '7.1'
s.osx.deployment_target = '10.9'
# Base directory where the .proto files are.
src = '.'
# We'll use protoc with the gRPC plugin.
s.dependency '!ProtoCompiler-gRPCPlugin', '~> 0.14'
# Pods directory corresponding to this app's Podfile, relative to the location of this podspec.
pods_root = '/Pods'
# Path where Cocoapods downloads protoc and the gRPC plugin.
protoc_dir = "#{pods_root}/!ProtoCompiler"
protoc = "#{protoc_dir}/protoc"
plugin = "#{pods_root}/!ProtoCompiler-gRPCPlugin/grpc_objective_c_plugin"
# Directory where you want the generated files to be placed. This is an example.
dir = "#{pods_root}/#{s.name}"
# Run protoc with the Objective-C and gRPC plugins to generate protocol messages and gRPC clients.
# You can run this command manually if you later change your protos and need to regenerate.
# Alternatively, you can advance the version of this podspec and run `pod update`.
s.prepare_command = <<-CMD
mkdir -p #{dir}
#{protoc} \
--plugin=protoc-gen-grpc=#{plugin} \
--objc_out=#{dir} \
--grpc_out=#{dir} \
-I #{src} \
-I #{protoc_dir} \
#{src}/*.proto
CMD
# The --objc_out plugin generates a pair of .pbobjc.h/.pbobjc.m files for each .proto file.
s.subspec 'Messages' do |ms|
ms.source_files = "#{dir}/*.pbobjc.{h,m}"
ms.header_mappings_dir = dir
ms.requires_arc = false
# The generated files depend on the protobuf runtime.
ms.dependency 'Protobuf'
# This is needed by all pods that depend on Protobuf:
ms.pod_target_xcconfig = {
'GCC_PREPROCESSOR_DEFINITIONS' => '$(inherited) GPB_USE_PROTOBUF_FRAMEWORK_IMPORTS=1',
}
end
# The --objcgrpc_out plugin generates a pair of .pbrpc.h/.pbrpc.m files for each .proto file with
# a service defined.
s.subspec 'Services' do |ss|
ss.source_files = "#{dir}/*.pbrpc.{h,m}"
ss.header_mappings_dir = dir
ss.requires_arc = true
# The generated files depend on the gRPC runtime, and on the files generated by `--objc_out`.
ss.dependency 'gRPC-ProtoRPC'
ss.dependency "#{s.name}/Messages"
end
end
```
The file should be named `.podspec`.
Note: If your proto files are in a directory hierarchy, you might want to adjust the _globs_ used in
the sample Podspec above. For example, you could use:
```ruby
s.prepare_command = <<-CMD
...
#{src}/*.proto #{src}/**/*.proto
CMD
...
ms.source_files = "#{dir}/*.pbobjc.{h,m}", "#{dir}/**/*.pbobjc.{h,m}"
...
ss.source_files = "#{dir}/*.pbrpc.{h,m}", "#{dir}/**/*.pbrpc.{h,m}"
```
Once your library has a Podspec, Cocoapods can install it into any XCode project. For that, go into
your project's directory and create a Podfile by running:
```sh
pod init
```
Next add a line to your Podfile to refer to your library's Podspec. Use `:path` as described
[here](https://guides.cocoapods.org/using/the-podfile.html#using-the-files-from-a-folder-local-to-the-machine):
```ruby
pod '', :path => 'path/to/the/directory/of/your/podspec'
```
You can look at this [example Podfile][].
Finally, in your project's directory, run:
```sh
pod install
```
## Use the generated library in your code
Please check the [example apps][] for examples of how to use a generated gRPC library.
## Use gRPC without Protobuf
This [tests file](https://github.com/grpc/grpc/tree/master/src/objective-c/tests/GRPCClientTests.m)
shows how to use the generic gRPC Objective-C client without generated protobuf files.
## Alternatives to the steps above
### Install _protoc_ with the gRPC plugin
Although it's not recommended (because it can lead to hard-to-solve version conflicts), it is
sometimes more convenient to install _protoc_ and the gRPC plugin in your development machine,
instead of letting Cocoapods download the appropriate versions for you. To do so, on Mac OS X or
later, install [homebrew][].
The run the following command to install _protoc_ and the gRPC _protoc_ plugin:
```sh
$ curl -fsSL https://goo.gl/getgrpc | bash -
```
This will download and run the [gRPC install script][].
### Install _protoc_ and the gRPC plugin without using Homebrew
First install v3 of the Protocol Buffers compiler (_protoc_), by cloning
[its Git repository](https://github.com/google/protobuf) and following these
[installation instructions](https://github.com/google/protobuf#c-installation---unix)
(the ones titled C++; don't miss the note for Mac users).
Then clone this repository and execute the following commands from the root directory where it was
cloned.
Compile the gRPC plugins for _protoc_:
```sh
make grpc_objective_c_plugin
```
Create a symbolic link to the compiled plugin binary somewhere in your `$PATH`:
```sh
ln -s `pwd`/bins/opt/grpc_objective_c_plugin /usr/local/bin/protoc-gen-objcgrpc
```
(Notice that the name of the created link must begin with "`protoc-gen-`" for _protoc_ to recognize
it as a plugin).
If you don't want to create the symbolic link, you can alternatively copy the binary (with the
appropriate name). Or you might prefer instead to specify the plugin's path as a flag when invoking
_protoc_, in which case no system modification nor renaming is necessary.
### Integrate the generated gRPC library without using Cocoapods
You need to compile the generated `.pbobjc.*` files (the enums and messages) without ARC support,
and the generated `.pbrpc.*` files (the services) with ARC support. The generated code depends on
v0.12+ of the Objective-C gRPC runtime library and v3.0.0-alpha-4+ of the Objective-C Protobuf
runtime library.
These libraries need to be integrated into your project as described in their respective Podspec
files:
* [Podspec](https://github.com/grpc/grpc/blob/master/gRPC.podspec) for the Objective-C gRPC runtime
library. This can be tedious to configure manually.
* [Podspec](https://github.com/google/protobuf/blob/master/Protobuf.podspec) for the
Objective-C Protobuf runtime library.
[Protocol Buffers]:https://developers.google.com/protocol-buffers/
[homebrew]:http://brew.sh
[gRPC install script]:https://raw.githubusercontent.com/grpc/homebrew-grpc/master/scripts/install
[example Podfile]:https://github.com/grpc/grpc/blob/master/examples/objective-c/helloworld/Podfile
[example apps]: https://github.com/grpc/grpc/tree/master/examples/objective-c