Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

677 lines (625 sloc) 22.433 kb
dir = File.dirname(__FILE__)
require "#{dir}/page"
require "#{dir}/navbar"
require "#{dir}/article"
require "#{dir}/section"
require "#{dir}/source"
class Userguide < Page
include Source
def initialize
super(:page_title => "User Guide")
end
def promo
"images/1959erector.jpeg"
end
def body_content
p do
text "Make sure to check out the ",
a("RDoc Documentation", :href => "rdoc"),
" for more details on the API."
end
widget article
end
def article
Article.new(:name => "Erector User Guide").tap { |a|
a.add(:name => "The Basics") do
p do
text "The basic way to construct some HTML/XML with erector is to subclass ",
code("Erector::Widget"),
" and implement a ",
code("content"),
" method:"
end
table do
tr do
td :valign => "top" do
source_code :ruby, <<-RUBY
class Hello < Erector::Widget
def content
html {
head {
title "Hello"
}
body {
text "Hello, "
b "world!"
}
}
end
end
RUBY
end
td do
span.separator do
text character(:rightwards_arrow)
end
end
td :valign => "top" do
source_code :html, <<-HTML
<html>
<head>
<title>Hello</title>
</head>
<body>
Hello, <b>world!</b>
</body>
</html>
HTML
end
end
end
p do
text "Once you have a widget class, you can instantiate it and then call its "
code "to_html"
text " method."
text " If you want to pass in parameters (aka 'assigns' or 'locals' in Rails parlance), then do so in the constructor's default hash. This will make instance variables of the same name, with Ruby's '@' sign."
end
source_code :ruby, <<-PRE
class Email < Erector::Widget
def content
a @address, :href => "mailto:\#{@address}"
end
end
>> Email.new(:address => "foo@example.com").to_html
=> "<a href=\\"mailto:foo@example.com\\">foo@example.com</a>"
PRE
p do
text "(If you want control over which locals are valid to be passed in to a widget, use the "
a "needs", :href => "#needs"
text " macro.)"
end
end
a.add(:name => "Mixin") do
p "If all this widget stuff is too complicated, just do "
pre "include Erector::Mixin"
p do
text "and then call "
code "erector { }"
text " from anywhere in your code. It will make an "
a "inline widget", :href => "#inline"
text " for you, pass in the block, and call "
code "to_html"
text " on it. And if you pass any options to "
code "erector"
text ", like "
code ":prettyprint => true"
text ", it'll pass them along to "
code "to_html"
text "!"
end
h3 "Examples:"
source_code :ruby, <<-PRE
erector { a "lols", :href => "http://icanhascheezburger.com/" }
=> "<a href=\\"http://icanhascheezburger.com/\\">lols</a>"
erector(:prettyprint => true) do
ol {
li "bacon"
li "lettuce"
li "tomato"
}
end
=> "<ol>\\n <li>bacon</li>\\n <li>lettuce</li>\\n <li>tomato</li>\\n</ol>\\n"
PRE
end
a.add(:name => "Pretty-printing") do
p "Erector has the ability to insert newlines and indentation to make the generated HTML more readable. Newlines are inserted before and after certain tags."
p "To enable pretty-printing (insertion of newlines and indentation) of Erector's output, do one of the following:"
ul do
li do
text "call "
code "to_pretty"
text " instead of "
code "to_html"
text " on your Erector::Widget"
end
li do
text "pass "
code ":prettyprint => true"
text " to "
code "to_html"
end
li do
text "call "
code "enable_prettyprint(true)"
text " on your Erector::Widget. Then subsequent calls to "
code "to_html"
text " will prettyprint"
end
li do
text "call "
code "Erector::Widget.prettyprint_default = true"
text " (for example, in environments/development.rb in a rails application, or anywhere which is convenient)"
end
end
end
a.add(:name => "Classes and IDs") do
p do
text "Because HTML tends to heavily use the "
code "class"
text " and "
code "id"
text " attributes, it is convenient to have a special syntax to specify them."
end
table do
tr do
td :valign => "top" do
source_code :ruby, <<-RUBY
body.sample!.helpful "Hello, world!"
RUBY
end
td do
span.separator do
text character(:rightwards_arrow)
end
end
td :valign => "top" do
source_code :html, <<-HTML
body class="helpful" id="sample"
HTML
end
end
end
p do
text "Most CSS and javascript tends to write classes and IDs with hyphens (for example "
code "nav-bar"
text " instead of "
code "nav_bar"
text "). Therefore, erector has a setting to convert underscores to hyphens."
end
table do
tr do
td :valign => "top" do
source_code :ruby, <<-RUBY
Erector::Widget.hyphenize_underscores = true
body.my_id!.nav_bar "Hello, world!"
RUBY
end
td do
span.separator do
text character(:rightwards_arrow)
end
end
td :valign => "top" do
source_code :html, <<-HTML
body class="nav-bar" id="my-id"
HTML
end
end
end
p do
text "You can put the setting of "
code "hyphenize_underscores"
text " anywhere it is convenient, for example "
code "config/application.rb"
text " in a rails application. For compatibility with erector 0.9.0, the "
text "default is false, but this is likely to change to true in a future version "
text "of erector, so explicitly set it to false if you are relying on the "
text "underscores."
end
end
a.add(:name => "Erector tool: Command-line conversion to and from HTML", :href => "tool") do
p """
We've written a little tool that will help you
erect your existing HTML app. The 'erector' tool will convert HTML or HTML/ERB into an Erector class.
It ships as part of the Erector gem, so to try it out, install the gem, then run
""".strip
pre "erector app/views/foos/*.html.erb"
p "or just"
pre "erector app/views"
p "and then delete the original files when you're satisfied."
p {
text "See the ", a("Erector on Rails Guide", :href => "rails.html"), " for more details on converting a Rails app."
}
p do
text "On the erector-to-html side, pass in the "
code "--to-html"
text "option and some file names and it will render the erector widgets to appropriately-named HTML files."
text " We're actually using "
code "erector"
text " to build this Erector documentation web site that you're reading "
b "right now."
text " Check out the ",
a("'web' directory", :href => "https://github.com/erector/erector/tree/master/web"),
" and the ",
a("'web' task in the Rakefile", :href => "https://github.com/erector/erector/blob/77738d13fbbb3e1b8d24653ff2950dbb88b756ed/Rakefile#L74-84"),
" to see how it's done."
end
end
a.add(:name => "Page Layout Inheritance") do
p "Erector replaces the typical Rails layout mechanism with a more natural construct, the use of inheritance. Want a common
layout? Implement a layout superclass and have your page class inherit from it and override methods as needed."
p do
text "For example:"
source_code :ruby, <<-RUBY
class MyAppPage < Erector::Widget
def content
html {
head {
title "MyApp - \#{@page_title}"
css "myapp.css"
}
body {
div.navbar {
navbar
}
div.main {
main
}
div.footer {
footer
}
}
}
end
def navbar
a "MyApp Home", :href => "/"
end
def main
p "This page intentionally left blank."
end
def footer
p "Copyright (c) 2112, Rush Enterprises Inc."
end
end
RUBY
source_code :ruby, <<-RUBY
class Faq < MyAppPage
def initialize
super(:page_title => "FAQ")
end
def main
p "Q: Why is the sky blue?"
p "A: To get to the other side"
end
def navbar
super
a "More FAQs", :href => "http://faqs.org"
end
end
RUBY
end
p "Notice how this mechanism allows you to..."
ul do
li "Set instance variables (e.g. title)"
li "Override sections completely (e.g. render_body)"
li "Append to standard content (e.g. render_navbar)"
li "Use standard content unchanged (e.g. render_footer)"
end
p "all in a straightforward, easily understood paradigm (OO inheritance). (No more weird yielding to invisible, undocumented closures!)"
p {
text "Check out "
a "Erector::Widgets::Page", :href => "/rdoc/Erector/Widgets/Page.html"
text " for a widget that does a lot of this for you, including rendering "
a "externals", :href => "#externals"
text " in the HEAD element."
}
end
a.add(:name => "Inline Widgets") do
p do
text "Instead of subclassing "
code "Erector::Widget"
text " and implementing a "
code "content"
text " method, you can pass a block to "
code "Erector.inline"
text " and get back a widget instance you can call "
code "to_html"
text " on. For example:"
source_code :ruby, <<-RUBY
hello = Erector.inline do
p "Hello, world!"
end
hello.to_html #=> <p>Hello, world!</p>
RUBY
text "This lets you define mini-widgets on the fly."
end
p do
text "If you're in Rails, your inline block has access to Rails helpers if you pass a helpers object to "
code "to_html"
text ":"
source_code :ruby, <<-RUBY
image = Erector.inline do
image_tag("/foo")
end
image.to_html(:helpers => controller) #=> <img alt="Foo" src="/foo" />
RUBY
end
p do
text "Note that inline widgets are usually redundant if you're already inside an Erector content method. You can just use a normal "
code "do"
text " block and the Erector methods will work as usual when called back from "
code "yield"
text ". Inline widgets get evaluated with "
code "instance_eval"
text " which may or may not be what you want. See the section on "
a "blocks", :href=>"#blocks"
text " in this user guide for more detail."
end
p do
text "One extra bonus feature of inline widgets is that they can call methods defined on the parent class, even though they're out of scope. How do they do this? Through method_missing magic. (But isn't method_missing magic against the design goals of Erector? Yes, some would say so, and that's why we're reserving it for a special subclass and method. For Erector::Widget and subclasses, if you pass in a block, it's a plain old block with normal semantics.) But they can't directly access instance variables on the parent, so watch it."
end
end
a.add(:name => "Needs") do
p do
text "Named parameters in Ruby are fun, but one frustrating aspect of the 'options hash' technique is that "
text "the code is less self-documenting and doesn't 'fail fast' if you pass in the wrong parameters, "
text "or fail to pass in the right ones. Even simple typos can lead to very annoying debugging problems."
end
p do
text "To help this, we've added an optional feature by which your widget can declare that it "
text "needs a certain set of named parameters to be passed in. "
text "For example:"
source_code :ruby, <<-RUBY
class Car < Erector::Widget
needs :engine, :wheels => 4
def content
text "My \#{@wheels} wheels go round and round; my \#{@engine} goes vroom!"
end
end
RUBY
text "This widget will throw an exception if you fail to pass "
code ":engine => 'V-8'"
text " into its constructor. (Actually, it will work with any engine, but a V-8 is the baddest.)"
end
p do
text "See the "
a "rdoc for Widget#needs", :href => 'rdoc/classes/Erector/Widget.html#M000053'
text " for more details. Note that as of version 0.7.0, using "
code "needs"
text " no longer automatically declares accessor methods."
end
end
a.add(:name => "Externals") do
p do
text "Erector's got some nice tags, like "
code "script"
text " and "
code "style"
text ", that you can emit in the content method of your widget. But what if your widget needs something, say a JavaScript library, that should be included not in the main page, but inside the "
code "head"
text " section?"
end
p do
a "Externals", :href => "rdoc/classes/Erector/Externals.html"
text " are a way for your widget to announce to the world that it has an external dependency. It's then up to "
a "another widget", :href => "rdoc/classes/Erector/Widgets/Page.html"
text " to emit that dependency while it's rendering the "
code "head"
text "."
end
p do
text "Here's an example:"
source_code :ruby, <<-RUBY
class HotSauce < Erector::Widget
depends_on :css, "/css/tapatio.css"
depends_on :css, "/css/salsa_picante.css", :media => "print"
depends_on :js, "/lib/jquery.js"
depends_on :js, "/lib/picante.js"
def content
p.hot_sauce {
text "esta salsa es muy picante!"
}
end
end
RUBY
text "Then when "
code "Page"
text " emits the "
code "head"
text " it'll look like this:"
source_code :ruby, <<-RUBY
<head>
<meta content="text/html;charset=UTF-8" http-equiv="content-type" />
<title>HotPage</title>
<link href="/css/tapatio.css" media="all" rel="stylesheet" type="text/css" />
<link href="/css/salsa_picante.css" media="print" rel="stylesheet" type="text/css" />
<script src="/lib/jquery.js" type="text/javascript"></script>
<script src="/lib/picante.js" type="text/javascript"></script>
</head>
RUBY
end
p do
text "It also collapses redundant externals, so if lots of your widgets declare the same thing (say, 'jquery.js'), it'll only get included once."
end
p do
a "Page", :href => "rdoc/classes/Erector/Widgets/Page.html"
text " looks for the following externals:"
table do
tr do
th ":js"
td "included JavaScript file"
end
tr do
th ":css"
td "included CSS stylesheet"
end
tr do
th ":script"
td "inline JavaScript"
end
tr do
th ":style"
td "inline CSS style"
end
end
text "It might be a little difficult to remember the difference between :js and :script, and between :css and :style, so I'm thinking of maybe unifying them and looking at the content to determine whether it's inline or not. (Something simple like, if it includes a space, then it's inline.) Good idea? Let us know on "
a "the erector mailing list", :href => "http://googlegroups.com/group/erector"
text "!"
end
p do
text "Instead of a string, you can also specify a File object; the file's contents get read and used as text. This allows you to inline files instead of referring to them, for potential performance benefits."
text " Example:"
source_code :ruby, <<-RUBY
depends_on :style, File.new("\#{File.dirname(__FILE__)}/../public/sample.css")
RUBY
end
end
a.add(:name => "Blocks") do
p "Erector is all about blocks (otherwise known as closures). Unfortunately, there are some confusing aspects to working with blocks; this section aims to clarify the issues so if you find yourself stuck on an 'undefined method' or a nil instance variable, at least you'll have some context to help debug it."
p "There are basically three cases where you can pass a block to Erector:"
h3 "1. To an element method"
p "This is the normal case that provides the slick HTML DSL. In the following code:"
source_code :ruby, <<-RUBY
class Person < Erector::Widget
def content
div {
h3 @name
p {
b "Birthday: "
span @birthday
}
}
end
end
RUBY
p do
text "the blocks passed in to "
code "div"
text " and "
code "p"
text " are evaluated using normal "
code "yield"
text " semantics, and the "
code "@name"
text " and "
code "@birthday"
text " instance variables are evaluated in the context of the Person instance being rendered."
end
p "So far, so good."
h3 "2. To the constructor of an Erector::Widget"
p do
text "In this case you can build a widget \"on the fly\" and have it render whatever it wants, then call your block. This is useful for widgets like "
code "Form"
text " which want to wrap your HTML in some of their own tags."
end
source_code :ruby, <<-RUBY
class PersonActions < Erector::Widget
needs :user
def content
div {
widget(Form.new(:action => "/person/\#{@user.id}", :method => "delete") {
input :type => "submit", :value => "Remove \#{@user.name}"
})
widget(Form.new(:action => "/person/\#{@user.id}/email", :method => "post") {
b "Send message: "
input :type => "text", :name => "message"
input :type => "submit", :value => "Email \#{@user.name}"
})
}
end
end
RUBY
p do
text "In this case, you will get two "
code "form"
text " elements, each of which has some boilerplate HTML for emitting the form element, emitting the hidden "
code "_method"
text " input tag in the case of the delete method, then calling back into your widget to emit the contents of the form. In this case, as above, the "
code "@user"
text " instance variable will be sought inside the "
b "calling"
text " widget"
code "(PersonActions)"
text ", not the "
b "called "
text " widget"
code "(Form)"
text "."
end
p do
text "A quirk of this technique is that methods inside the block will be called on the calling widget, not the called widget. This doesn't cause any problems for element methods ("
code "b"
text " and "
code "input"
text " above"
text "), but may be confusing if you want the block to be able to call methods on the target widget. In that case the caller can declare the block to take a parameter; this parameter will point to the nested widget instance."
source_code :ruby, <<-RUBY
widget(Form.new(:action => "/person/\#{@user.id}", :method => "delete") do |f|
span "This form's method is \#{f.method}"
input :type => "submit", :value => "Remove \#{@user.name}"
end)
RUBY
end
p do
text "(As a variant of this case, note that the"
code "widget"
text " method can accept a widget class, hash and block, instead of an instance; in this case it will set the widget's block and this code:"
source_code :ruby, <<-RUBY
widget Form, :action => "/person/\#{@user.id}", :method => "delete" do
input :type => "submit", :value => "Remove \#{@user.name}"
end
RUBY
text " will work the same as the version above.)"
end
h3 "3. To the constructor of an Erector::InlineWidget"
p do
text "This is where things get hairy. Sometimes we want to construct a widget on the fly, but we're not inside a widget already. So any block we pass in will not have access to Erector methods. In this case we have a special subclass called "
code "Erector::InlineWidget"
text " which uses two magic tricks: "
code "instance_eval"
text " and "
code "method_missing"
text " to accomplish the following:"
ul do
li do
text "inside the block, "
code "self"
text " points to the widget, not the caller."
end
li do
text "methods will be looked for first on the inline widget, and then on the caller."
end
li do
text "instance variables will be looked for on the inline widget "
b "only"
text ". This can be the source of many a nil! As a general rule, you should probably stay away from instance variables when using inline widgets. However..."
end
li do
b "Bound"
text " local variables will still be in scope. This means you can \"smuggle in\" instance variables via local variables. For example:"
source_code :ruby, <<-RUBY
local_name = @name
Page.new do
div local_name
end.to_html
RUBY
end
end
p do
text "When using the "
a "mixin", :href => "#mixin"
text ", you get an inline widget, so the above list of tricks applies."
end
hr
p do
text "One note for developers: when creating a widget like "
code "Form"
text " that needs to call back to its block, use the method "
code "call_block"
text ", which calls the block and passes in self as appropriate for both inline and normal widgets."
end
end
end
}
end
end
Jump to Line
Something went wrong with that request. Please try again.