React-Rails - problems getting started

问题:

I'm trying to figure out how to use react-rails with my Rails 5 gem.

At the moment, I'm trying to follow the tutorial in this post. https://medium.com/technically-speaking/isomorphic-reactjs-app-with-ruby-on-rails-part-1-server-side-rendering-8438bbb1ea1c#.iwd44r60v

I can't get the page to render at present. I use app_roles instead of posts, but otherwise I've followed the steps shown in the tutorial.

I have two files in my app/assets/javascripts/components folder.

app_role.js.jsx has:

var AppRole = React.createClass({
    render: function() {
        return (
            <div className="h2">
                <AppRoleHeader app_role={this.props.app_role} />
                <AppRoleContent app_role={this.props.app_role} />
            </div>
        );
    }
});
var AppRoleHeader = React.createClass({
    render: function() {
        return (
            <div className="label">
                <h2>{this.props.app_role.title}</h2>
                <div className="label">
                    By {this.props.app_role.title} – {this.props.app_role.created_at}
                </div>
            </div>
        );
    }
});

var AppRoleContent = React.createClass({
    render: function() {
        return (
            <div className="label">
                {this.props.app_role.display_name}
            </div>
        );
    }
});

app_roles_list.js.jsx has:

var AppRolesList = React.createClass({
    getInitialState: function() {
        return { posts: this.props.initialAppRoles };
    },

    render: function() {
        var posts = this.state.app_roles.map(function(app_role) {
            return <AppRole key={app_role.id} app_role={app_role} />;
        });

        return (
            <div className="label">
                {app_roles}
            </div>
        );
    }
});

When I try to render this in my app_roles/index.html.erb file with:

<%= react_component('AppRolesList',
                    { initialAppRoles: @app_roles },
                    { prerender: params[:noprerender].nil? }) %>

I get an error that says:

ExecJS::RuntimeError at /app_roles
/private/var/folders/75/70zm4s4j14q74tfqpjvh49s80000gp/T/execjs20161015-7497-1bhq2x0js:24066
        return <div className="h2">
               ^

SyntaxError: Unexpected token <
    at exports.runInThisContext (vm.js:53:16)
    at Module._compile (module.js:373:25)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Function.Module.runMain (module.js:441:10)
    at startup (node.js:139:18)
    at node.js:974:3

I don't understand this error message. I've read some posts describing a problem where the return method has two elements being returned. I tried removing the div h2 tag altogether and putting the two returned elements in an array, but that didn't work either.

I have also read posts describing problems configuring babel. I don't follow the gist of those comments. In my config development.rb, I have:

config.react.variant = :development
  config.react.addons = true
  config.react.jsx_transform_options = {
    blacklist: ['spec.functionName', 'validation.react', 'strict'], # default options
    # optional: ["transformerName"],  # pass extra babel options
    whitelist: ["useStrict"] # even more options
  }

I'm not sure what I'm supposed to write in the optional: field. I assumed react-rails would give me some kind of default settings that would automatically work.

I also tried adding:

/** @jsx React.DOM */

to the top of each of the component files. Although that makes no difference to the problem.

I also tried adding this to config/application.rb

config.react.jsx_transformer_class = React::JSX::JSXTransformer

That doesn't change anything either.

I also tried adding this on my command line:

npm install --save-dev babel-preset-react

It made no difference to this problem.

Can anyone see what I need to do to get this page to load?

Application.js has:

//= require jquery
//= require jquery_ujs
//= require tether
//= require bootstrap-sprockets
//= require turbolinks
//= require react
//= require react_ujs
// require react_bootstrap
//= require components
//= require_tree .

回答1:

Couple of things to fix:

var AppRolesList = React.createClass({
    getInitialState: function() {
        return { posts: this.props.initialAppRoles };
    },

    render: function() {
        var posts = this.state.app_roles.map(function(app_role) {
            return <AppRole key={app_role.id} app_role={app_role} />;
        });

        return (
            <div className="label">
                {app_roles}
            </div>
        );
    }
});

You are copying the initialAppRoles prop into the posts state variable (which is mostly an anti-pattern), but then you expect this.state.app_roles which is never set.

You should just delete the whole getInitialState function here and directly use:

var posts = this.props.initialAppRoles.map(function(app_role) {
  return <AppRole key={app_role.id} app_role={app_role} />;
});

Second bug to fix: you are creating an array of posts in the render function, but then you have app_roles in your return which is not set. Correct that to have:

return (
  <div className="label">
    {posts}
  </div>
);

I copied pasted your code into my Rails setup (which uses react-rails) and it worked with prerendering on and off.

On a side note, I strongly recommend having one component per .js.jsx file with the underscore cased name of the component as its name. It'll make things easier to find in the future.