Class: FatCore::Evaluator

Inherits:
Object
  • Object
show all
Defined in:
lib/fat_core/evaluator.rb

Overview

The Evaluator class provides a class for evaluating Ruby expressions based on variable settings provided at runtime. If the same Evaluator object is used for several successive calls, it can maintain state between calls with instance variables. The call to Evaluator.new can be given a hash of instance variable names and values that will be maintained across all calls to the #evaluate method. In addition, on each evaluate call, a set of /local/ variables can be supplied to provide variables that exist only for the duration of that evaluate call. An optional before and after string can be given to the constructor that will evaluate the given expression before and, respectively, after each call to #evaluate. This provides a way to update values of instance variables for use in subsequent calls to #evaluate.

Instance Method Summary collapse

Constructor Details

#initialize(vars: {}, before: nil, after: nil) ⇒ Evaluator

Returns a new instance of Evaluator.

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# File 'lib/fat_core/evaluator.rb', line 15

def initialize(vars: {}, before: nil, after: nil)
  @before = before
  @after = after
  set_instance_vars(vars)
end

Instance Method Details

#evaluate(expr = '', vars: {}) ⇒ Object

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# File 'lib/fat_core/evaluator.rb', line 34

def evaluate(expr = '', vars: {})
  bdg = binding
  set_local_vars(vars, bdg)
  eval(@before, bdg) if @before
  result = eval(expr, bdg)
  eval(@after, bdg) if @after
  result
end

#set_instance_vars(vars = {}) ⇒ Object

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# File 'lib/fat_core/evaluator.rb', line 21

def set_instance_vars(vars = {})
  vars.each_pair do |name, val|
    name = "@#{name}" unless name.to_s.start_with?('@')
    instance_variable_set(name, val)
  end
end

#set_local_vars(vars = {}, bnd) ⇒ Object

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# File 'lib/fat_core/evaluator.rb', line 28

def set_local_vars(vars = {}, bnd)
  vars.each_pair do |name, val|
    bnd.local_variable_set(name, val)
  end
end