一、环境配置
(1)需要一台Mac(OSX)
(2)在Mac上安装Xcode
(3)安装node.js:https://nodejs.org/download/
(4)建议安装watchman，终端命令：brew install watchman
(5)安装flow：brew install flow
ok，按照以上步骤，你应该已经配置好了环境。
二、Hello, React-Native
现在我们需要创建一个React-Native的项目，因此可以按照下面的步骤：
打开终端，开始React-Native开发的旅程吧。
(1)安装命令行工具：sudo npm install -g react-native-cli
(2)创建一个空项目：react-native init HelloWorld
(3)找到创建的HelloWorld项目,双击HelloWorld.xcodeproj即可在xcode中打开项目。xcodeproj是xcode的项目文件。
(4)在xcode中，使用快捷键cmd R即可启动项目。基本的Xcode功能可以熟悉，比如模拟器的选择等。
启动完成后，你会看到React-Packger和iOS模拟器，具体的效果如下，说明你创建项目成功了。
Xcode10 上创建RN工程报错：error: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src: Permission deniederror: couldn't create directory /Users/dmy/HelloWorld/node_modules/react-native/third-party/glog-0.3.5/src:
解决办法：
不要直接使用 react-native init HelloWorld 创建项目,
后面加个 --version 0.45.0 之前的版本就好了,
比如:
react-native init HelloWorld --version 0.44.0
