Inject code that executes after the target instance method.
@param target_method
target_method
@param block
@note
Either method_sym or block is required.
@api public
# File lib/extlib/hook.rb, line 110 110: def after(target_method, method_sym = nil, &block) 111: install_hook :after, target_method, method_sym, :instance, &block 112: end
Inject code that executes after the target class method.
@param target_method
@note
Either method_sym or block is required.
@api public
# File lib/extlib/hook.rb, line 78 78: def after_class_method(target_method, method_sym = nil, &block) 79: install_hook :after, target_method, method_sym, :class, &block 80: end
— Helpers —
# File lib/extlib/hook.rb, line 384 384: def args_for(method) 385: if method.arity == 0 386: "&block" 387: elsif method.arity > 0 388: "_" << (1 .. method.arity).to_a.join(", _") << ", &block" 389: elsif (method.arity + 1) < 0 390: "_" << (1 .. (method.arity).abs - 1).to_a.join(", _") << ", *args, &block" 391: else 392: "*args, &block" 393: end 394: end
Inject code that executes before the target instance method.
@param target_method
target_method
@param block
@note
Either method_sym or block is required.
@api public
# File lib/extlib/hook.rb, line 94 94: def before(target_method, method_sym = nil, &block) 95: install_hook :before, target_method, method_sym, :instance, &block 96: end
Inject code that executes before the target class method.
@param target_method
target_method
@param block
@note
Either method_sym or block is required.
@api public
# File lib/extlib/hook.rb, line 63 63: def before_class_method(target_method, method_sym = nil, &block) 64: install_hook :before, target_method, method_sym, :class, &block 65: end
# File lib/extlib/hook.rb, line 155 155: def class_hooks 156: self.const_get("CLASS_HOOKS") 157: end
# File lib/extlib/hook.rb, line 283 283: def define_advised_method(target_method, scope) 284: args = args_for(method_with_scope(target_method, scope)) 285: 286: renamed_target = hook_method_name(target_method, 'hookable_', 'before_advised') 287: 288: source = def #{target_method}(#{args}) retval = nil catch(:halt) do #{hook_method_name(target_method, 'execute_before', 'hook_stack')}(#{args}) retval = #{renamed_target}(#{args}) #{hook_method_name(target_method, 'execute_after', 'hook_stack')}(retval, #{args}) retval end end 289: 290: if scope == :instance && !instance_methods(false).any? { |m| m.to_sym == target_method } 291: send(:alias_method, renamed_target, target_method) 292: 293: proxy_module = Module.new 294: proxy_module.class_eval(source, __FILE__, __LINE__) 295: self.send(:include, proxy_module) 296: else 297: source = %{alias_method :#{renamed_target}, :#{target_method}\n#{source}} 298: source = %{class << self\n#{source}\nend} if scope == :class 299: class_eval(source, __FILE__, __LINE__) 300: end 301: end
Defines two methods. One method executes the before hook stack. The other executes the after hook stack. This method will be called many times during the Class definition process. It should be called for each hook that is defined. It will also be called when a hook is redefined (to make sure that the arity hasn’t changed).
# File lib/extlib/hook.rb, line 233 233: def define_hook_stack_execution_methods(target_method, scope) 234: unless registered_as_hook?(target_method, scope) 235: raise ArgumentError, "#{target_method} has not be registered as a hookable #{scope} method" 236: end 237: 238: hooks = hooks_with_scope(scope) 239: 240: before_hooks = hooks[target_method][:before] 241: before_hooks = before_hooks.map{ |info| inline_call(info, scope) }.join("\n") 242: 243: after_hooks = hooks[target_method][:after] 244: after_hooks = after_hooks.map{ |info| inline_call(info, scope) }.join("\n") 245: 246: before_hook_name = hook_method_name(target_method, 'execute_before', 'hook_stack') 247: after_hook_name = hook_method_name(target_method, 'execute_after', 'hook_stack') 248: 249: hooks[target_method][:in].class_eval #{scope == :class ? 'class << self' : ''} private remove_method :#{before_hook_name} if instance_methods(false).any? { |m| m.to_sym == :#{before_hook_name} } def #{before_hook_name}(*args) #{before_hooks} end remove_method :#{after_hook_name} if instance_methods(false).any? { |m| m.to_sym == :#{after_hook_name} } def #{after_hook_name}(*args) #{after_hooks} end #{scope == :class ? 'end' : ''}, __FILE__, __LINE__ + 1 250: end
Generates names for the various utility methods. We need to do this because the various utility methods should not end in = so, while we’re at it, we might as well get rid of all punctuation.
# File lib/extlib/hook.rb, line 203 203: def hook_method_name(target_method, prefix, suffix) 204: target_method = target_method.to_s 205: 206: case target_method[1,1] 207: when '?' then "#{prefix}_#{target_method[0..-2]}_ques_#{suffix}" 208: when '!' then "#{prefix}_#{target_method[0..-2]}_bang_#{suffix}" 209: when '=' then "#{prefix}_#{target_method[0..-2]}_eq_#{suffix}" 210: # I add a _nan_ suffix here so that we don't ever encounter 211: # any naming conflicts. 212: else "#{prefix}_#{target_method[0..-1]}_nan_#{suffix}" 213: end 214: end
Returns the correct HOOKS Hash depending on whether we are working with class methods or instance methods
# File lib/extlib/hook.rb, line 147 147: def hooks_with_scope(scope) 148: case scope 149: when :class then class_hooks 150: when :instance then instance_hooks 151: else raise ArgumentError, 'You need to pass :class or :instance as scope' 152: end 153: end
Returns ruby code that will invoke the hook. It checks the arity of the hook method and passes arguments accordingly.
# File lib/extlib/hook.rb, line 270 270: def inline_call(method_info, scope) 271: Extlib::Hook::ClassMethods.hook_scopes << method_info[:from] 272: name = method_info[:name] 273: 274: if scope == :instance 275: args = method_defined?(name) && instance_method(name).arity != 0 ? '*args' : '' 276: %(#{name}(#{args}) if self.class <= Extlib::Hook::ClassMethods.object_by_id(#{method_info[:from].object_id})) 277: else 278: args = respond_to?(name) && method(name).arity != 0 ? '*args' : '' 279: %(#{name}(#{args}) if self <= Extlib::Hook::ClassMethods.object_by_id(#{method_info[:from].object_id})) 280: end 281: end
— Add a hook —
# File lib/extlib/hook.rb, line 315 315: def install_hook(type, target_method, method_sym, scope, &block) 316: assert_kind_of 'target_method', target_method, Symbol 317: assert_kind_of 'method_sym', method_sym, Symbol unless method_sym.nil? 318: assert_kind_of 'scope', scope, Symbol 319: 320: if !block_given? and method_sym.nil? 321: raise ArgumentError, "You need to pass 2 arguments to \"#{type}\"." 322: end 323: 324: if method_sym.to_s[1,1] == '=' 325: raise ArgumentError, "Methods ending in = cannot be hooks" 326: end 327: 328: unless [ :class, :instance ].include?(scope) 329: raise ArgumentError, 'You need to pass :class or :instance as scope' 330: end 331: 332: if registered_as_hook?(target_method, scope) 333: hooks = hooks_with_scope(scope) 334: 335: #if this hook is previously declared in a sibling or cousin we must move the :in class 336: #to the common ancestor to get both hooks to run. 337: if !(hooks[target_method][:in] <=> self) 338: before_hook_name = hook_method_name(target_method, 'execute_before', 'hook_stack') 339: after_hook_name = hook_method_name(target_method, 'execute_after', 'hook_stack') 340: 341: hooks[target_method][:in].class_eval remove_method :#{before_hook_name} if instance_methods(false).any? { |m| m.to_sym == :#{before_hook_name} } def #{before_hook_name}(*args) super end remove_method :#{after_hook_name} if instance_methods(false).any? { |m| m.to_sym == :#{before_hook_name} } def #{after_hook_name}(*args) super end, __FILE__, __LINE__ + 1 342: 343: while !(hooks[target_method][:in] <=> self) do 344: hooks[target_method][:in] = hooks[target_method][:in].superclass 345: end 346: 347: define_hook_stack_execution_methods(target_method, scope) 348: hooks[target_method][:in].class_eval{define_advised_method(target_method, scope)} 349: end 350: else 351: register_hook(target_method, scope) 352: hooks = hooks_with_scope(scope) 353: end 354: 355: #if we were passed a block, create a method out of it. 356: if block 357: method_sym = "__hooks_#{type}_#{quote_method(target_method)}_#{hooks[target_method][type].length}".to_sym 358: if scope == :class 359: meta_class.instance_eval do 360: define_method(method_sym, &block) 361: end 362: else 363: define_method(method_sym, &block) 364: end 365: end 366: 367: # Adds method to the stack an redefines the hook invocation method 368: hooks[target_method][type] << { :name => method_sym, :from => self } 369: define_hook_stack_execution_methods(target_method, scope) 370: end
# File lib/extlib/hook.rb, line 159 159: def instance_hooks 160: self.const_get("INSTANCE_HOOKS") 161: end
# File lib/extlib/hook.rb, line 396 396: def method_with_scope(name, scope) 397: case scope 398: when :class then method(name) 399: when :instance then instance_method(name) 400: else raise ArgumentError, 'You need to pass :class or :instance as scope' 401: end 402: end
This will need to be refactored
# File lib/extlib/hook.rb, line 217 217: def process_method_added(method_name, scope) 218: hooks_with_scope(scope).each do |target_method, hooks| 219: if hooks[:before].any? { |hook| hook[:name] == method_name } 220: define_hook_stack_execution_methods(target_method, scope) 221: end 222: 223: if hooks[:after].any? { |hook| hook[:name] == method_name } 224: define_hook_stack_execution_methods(target_method, scope) 225: end 226: end 227: end
# File lib/extlib/hook.rb, line 404 404: def quote_method(name) 405: name.to_s.gsub(/\?$/, '_q_').gsub(/!$/, '_b_').gsub(/=$/, '_eq_') 406: end
Register a class method as hookable. Registering a method means that before hooks will be run immediately before the method is invoked and after hooks will be called immediately after the method is invoked.
@param hookable_method
be hookable
@api public
# File lib/extlib/hook.rb, line 122 122: def register_class_hooks(*hooks) 123: hooks.each { |hook| register_hook(hook, :class) } 124: end
Registers a method as hookable. Registering hooks involves the following process
Create a blank entry in the HOOK Hash for the method.
Define the methods that execute the before and after hook stack. These methods will be no-ops at first, but everytime a new hook is defined, the methods will be redefined to incorporate the new hook.
Redefine the method that is to be hookable so that the hook stacks are invoked approprietly.
# File lib/extlib/hook.rb, line 172 172: def register_hook(target_method, scope) 173: if scope == :instance && !method_defined?(target_method) 174: raise ArgumentError, "#{target_method} instance method does not exist" 175: elsif scope == :class && !respond_to?(target_method) 176: raise ArgumentError, "#{target_method} class method does not exist" 177: end 178: 179: hooks = hooks_with_scope(scope) 180: 181: if hooks[target_method].nil? 182: hooks[target_method] = { 183: # We need to keep track of which class in the Inheritance chain the 184: # method was declared hookable in. Every time a child declares a new 185: # hook for the method, the hook stack invocations need to be redefined 186: # in the original Class. See #define_hook_stack_execution_methods 187: :before => [], :after => [], :in => self 188: } 189: 190: define_hook_stack_execution_methods(target_method, scope) 191: define_advised_method(target_method, scope) 192: end 193: end
Register aninstance method as hookable. Registering a method means that before hooks will be run immediately before the method is invoked and after hooks will be called immediately after the method is invoked.
@param hookable_method
be hookable
@api public
# File lib/extlib/hook.rb, line 134 134: def register_instance_hooks(*hooks) 135: hooks.each { |hook| register_hook(hook, :instance) } 136: end
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