const_defined? & const_get, class_eval, instance_methods

Module api
<br />#可以檢視有沒有這個常數<br />Object.const_defined?('BACKOFFICE_IMAGE_HOST')<br /><br />#get 這個常數<br />Object.const_get('BACKOFFICE_IMAGE_HOST')<br /><br />#也可以 set<br /> Math.const_set("HIGH_SCHOOL_PI", 22.0/7.0) #=> 3.14285714285714<br /> Math::HIGH_SCHOOL_PI - Math::PI #=> 0.00126448926734968<br /><br />#有instance_methods 這種好東西<br />>> User.instance_methods.find_all{|m| m =~/perf/}<br />=> ["year_to_date_perf", "perf", "user_overall_perf", "today_perf", "one_week_perf", "one_month_perf", "three_month_perf", "signals_with_distinct_target_by_perf", "performance", "six_month_perf", "performance=", "one_year_perf", "month_to_date_perf"]<br /><br />#module_eval<br /> class Thing<br /> end<br /> a = %q{def hello() "Hello there!" end}<br /> Thing.module_eval(a)<br /> puts Thing.new.hello()<br /> Thing.module_eval("invalid code", "dummy", 123)<br /><br /><br />#define_method, 動態生method的好物<br /> PERFORMACE_KEY_INTEGER = [<br /> :total, :rank, :success_num, :success_total<br /> ]<br /> <br /> PERFORMACE_KEY_INTEGER.flatten.each do |m|<br /> define_method(m, lambda {<br /> perf = performance<br /> perf ? perf[m].to_i : nil<br /> })<br /> end<br /><br />#included, class_eval<br />module ForumMixin<br /><br /> def self.included(klass)<br /> klass.class_eval do<br /> before_filter :require_admin, :only => [:delete]<br /> before_filter :require_login, :only => [:create]<br /> end<br /> end<br /><br />end<br /><br />#method_defined? 也是好物<br />