Class: TExp::EvalEnvironment

Inherits:

Object

• Object
• TExp::EvalEnvironment

Includes:

DSL

Defined in:

lib/texp/dsl.rb

Overview

Internal class that provides an evaluation environment for temporal expressions. The temporal expression DSL methods are not generally exposed outside of the TExp module, meaning that any coded temporal expression must be prefixed with the TExp module name. This is cumbersome for a DSL.

One solution is to just include the TExp module wherever you wish to use temporal expressions. Including at the top level would make them available everywhere, but would also pollute the top level namespace with all of TExp’s methods.

An alternate solution is to use a block that is instance_eval’ed in the TExp namespace. Within in the block you can reference the TExp DSL methods freely, but they do not pollute any namespaces outside the block.

Unfortunately, the instance_eval technique will cut off access to methods defined in the calling namespace (since we are using TExp’s environment instead). The EvalEnvironment handles this by directing any unknown methods to the calling environment, making the instance_eval technique much more friendly.

See the texp method to see how this class is used.

Instance Method Summary

• #initialize(containing_env) ⇒ EvalEnvironment constructor

  Create a TExp environment for evaluating temporal expressions.

• #method_missing(sym, *args, &block) ⇒ Object

  The methods identified by sym is not found in the TExp namespace.

Methods included from DSL

#day, #dow, #evaluate_expression_in_environment, #every, #month, #normalize_units, #on, #week, #year

Constructor Details

#initialize(containing_env) ⇒ EvalEnvironment

Create a TExp environment for evaluating temporal expressions. Use the block binding to find the object where the block is embeded.

# File 'lib/texp/dsl.rb', line 314

def initialize(containing_env)
  @container = eval "self", containing_env
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(sym, *args, &block) ⇒ Object

The methods identified by sym is not found in the TExp namespace. Try calling it in the containing namespace.

# File 'lib/texp/dsl.rb', line 320

def method_missing(sym, *args, &block)
  @container.send(sym, *args, &block)
end