class Grizzled::String::Template::TemplateBase

Base (abstract) class for a string template. Common logic is here. Subclasses implement specific methods.

Attributes

resolver[R]

safe[R]

Public Class Methods

new(resolver, options={}) click to toggle source

Initializer.

Parameters:

resolver: A hash-like object that can take a variable name (via the +[]+ function) and resolve its value, returning the value (which is converted to string) or nil.
options: hash of options. See below.

Options:

:safe: true for a safe template that substitutes a blank string for a non-existent variable, instead of throwing an exception. Defaults to true.

# File lib/grizzled/string/template.rb, line 94
def initialize(resolver, options={})
  @resolver = resolver
  @safe = options.fetch(:safe, true)
end

Public Instance Methods

find_variable_ref(s) click to toggle source

Parse the location of the first variable in the string. Subclasses should override this method.

Parameters:

s: the string

Returns a Variable object, or nil.

# File lib/grizzled/string/template.rb, line 141
def find_variable_ref(s)
  nil
end

get_variable(name, default) click to toggle source

Get a variable's value, returning the empty string or throwing an exception, depending on the setting of safe.

Parameters:

name: Variable name
default: Default value, or nil

# File lib/grizzled/string/template.rb, line 152
def get_variable(name, default)
  
  def handle_no_value(default, name)
    if not default.nil?
      default
    elsif @safe
      ""
    else
      raise VariableNotFoundException.new(name)
    end
  end

  resolver[name] || handle_no_value(default, name)
end

handle_no_value(default, name) click to toggle source

# File lib/grizzled/string/template.rb, line 154
def handle_no_value(default, name)
  if not default.nil?
    default
  elsif @safe
    ""
  else
    raise VariableNotFoundException.new(name)
  end
end

substitute(s) click to toggle source

Replace all variable references in the given string. Variable references are recognized per the regular expression passed to the constructor. If a referenced variable is not found in the resolver, this method either:

throws a VariableNotFoundException (if safe is false).
substitutes an empty string (if safe is true)

Recursive references are supported (but beware of infinite recursion).

Parameters:

s: the string in which to replace variable references

Returns the substituted result.

# File lib/grizzled/string/template.rb, line 114
def substitute(s)

  def substitute_variable(var, s)
    end_string = var.iend == s.length ? "" : s[var.iend..-1]
    value = get_variable(var.name, var.default)
    transformed = 
      (var.istart == 0 ? "" : s[0..(var.istart-1)]) + value + end_string
    substitute(transformed)
  end

  # Locate the next variable reference.
  var = find_variable_ref(s)
  if var.nil?
    s
  else
    substitute_variable(var, s)
  end
end

substitute_variable(var, s) click to toggle source

# File lib/grizzled/string/template.rb, line 116
def substitute_variable(var, s)
  end_string = var.iend == s.length ? "" : s[var.iend..-1]
  value = get_variable(var.name, var.default)
  transformed = 
    (var.istart == 0 ? "" : s[0..(var.istart-1)]) + value + end_string
  substitute(transformed)
end