Class: Reek::SmellDetectors::UtilityFunction

Inherits:
BaseDetector show all
Defined in:
lib/reek/smell_detectors/utility_function.rb

Overview

A Utility Function is any instance method that has no dependency on the state of the instance.

Currently UtilityFunction will warn about any method that:

  • is non-empty, and

  • does not override an inherited method, and

  • calls at least one method on another object, and

  • doesn’t use any of self’s instance variables, and

  • doesn’t use any of self’s methods

A Utility Function often arises because it must manipulate other objects (usually its arguments) to get them into a useful form; one force preventing them (the arguments) doing this themselves is that the common knowledge lives outside the arguments, or the arguments are of too basic a type to justify extending that type. Therefore there must be something which ‘knows’ about the contents or purposes of the arguments. That thing would have to be more than just a basic type, because the basic types are either containers which don’t know about their contents, or they are single objects which can’t capture their relationship with their fellows of the same type. So, this thing with the extra knowledge should be reified into a class, and the utility method will most likely belong there.

If the method does refer to self, but refers to some other object more, FeatureEnvy is reported instead.

See Utility-Function for details.

Constant Summary collapse

PUBLIC_METHODS_ONLY_KEY = 
'public_methods_only'
PUBLIC_METHODS_ONLY_DEFAULT = 
false

Constants inherited from BaseDetector

BaseDetector::DEFAULT_EXCLUDE_SET, BaseDetector::EXCLUDE_KEY

Instance Attribute Summary

Attributes inherited from BaseDetector

#config, #context

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from BaseDetector

#config_for, configuration_keys, descendants, #enabled?, #exception?, #expression, inherited, #initialize, #run, smell_type, #smell_type, #smell_warning, #source_line, to_detector, todo_configuration_for, #value

Constructor Details

This class inherits a constructor from Reek::SmellDetectors::BaseDetector

Class Method Details

.contexts ⇒ Object

:nodoc:



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# File 'lib/reek/smell_detectors/utility_function.rb', line 49

def contexts # :nodoc:
  [:def]
end

.default_config ⇒ Object 



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# File 'lib/reek/smell_detectors/utility_function.rb', line 44

def self.default_config
  super.merge(PUBLIC_METHODS_ONLY_KEY => PUBLIC_METHODS_ONLY_DEFAULT)
end

Instance Method Details

#ignore_method? ⇒ Boolean (private)

Returns:

  • (Boolean) 


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# File 'lib/reek/smell_detectors/utility_function.rb', line 76

def ignore_method?
  context.non_public_visibility? &&
    value(PUBLIC_METHODS_ONLY_KEY, context)
end

#num_helper_methods ⇒ Object (private) 



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# File 'lib/reek/smell_detectors/utility_function.rb', line 72

def num_helper_methods
  context.local_nodes(:send).to_a.length
end

#sniff ⇒ Array<SmellWarning>

Checks whether the given method is a utility function.

Returns:



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# File 'lib/reek/smell_detectors/utility_function.rb', line 59

def sniff
  return [] if context.singleton_method? || context.module_function?
  return [] if context.references_self?
  return [] if num_helper_methods.zero?
  return [] if ignore_method?

  [smell_warning(
    lines: [source_line],
    message: "doesn't depend on instance state (maybe move it to another class?)")]
end