Tas

Trees as strings

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An instance of Tas represents a tree of similar objects, together with a reducing function. The goal of the reducing function is to reach a string representation of the tree, and that's why the reduction triggering method is to_s. The inspect method is an alias of to_s, with the consequence that the result of applying the reducing function becomes the object's representation.

Let's start with a trivial example:

view = Tas.new do |params|
  params.to_s
end

view[:foo] = 1
view[:bar] = 2

assert_equal view.to_s, "{:foo=>1, :bar=>2}"

We can use other instances of Tas as leaves:

foo = Tas.new do |params|
  params.to_s
end

bar = Tas.new do |params|
  params.to_s
end

baz = Tas.new do |params|
  params.to_s
end

foo[:a] = 1
foo[:b] = bar

bar[:c] = 2
bar[:d] = baz

baz[:e] = 3
baz[:f] = 4

assert_equal foo.to_s, "{:a=>1, :b=>{:c=>2, :d=>{:e=>3, :f=>4}}}"

To avoid the repeated definition of the reducing function, you can create a new Tas instance from an existing one:

foo = Tas.new do |params|
  params.to_s
end

bar = foo.new
baz = bar.new

foo[:bar] = bar
bar[:baz] = baz

assert_equal foo.to_s, "{:bar=>{:baz=>{}}}"

The following example renders some views with Mote:

require "tas"
require "mote"

# Create a viewer and define the rendering function
viewer = Tas.new do |params|
  mote(params[:src], params)
end

# Create two different components
page = viewer.new
view = viewer.new

# Each component has its own template
page[:src] = "views/layout.mote"
view[:src] = "views/index.mote"

# Both components have a title
page[:title] = "Hello"
view[:title] = "Welcome!"

# Insert one component into another
page[:content] = view

# Render all components
page.to_s

params: Hash with components.

reduce: Function for processing the params hash.

new: Create a new instance and propagate the reduce function.

[](marker): Return the component at params[marker].

[]=(marker, component): Assign the component to params[marker].

fetch(marker): Return the element at params[marker] or raise if the element is not present.

If no reduce function was defined, an attempt to call to_s will raise the Tas::ReduceMissing exception.

An attempt to fetch an undefined marker will raise the Tas::MarkerMissing exception.

$ gem install tas