Ruby Kernel.set_trace_func用法及代码示例

Establishes _proc_ as the handler for tracing, or disables
tracing if the parameter is +nil+.

*Note:* this method is obsolete, please use TracePoint instead.

_proc_ takes up to six parameters:

*   an event name
*   a filename
*   a line number
*   an object id
*   a binding
*   the name of a class

_proc_ is invoked whenever an event occurs.

Events are:

+c-call+:: call a C-language routine
+c-return+:: return from a C-language routine
+call+:: call a Ruby method
+class+:: start a class or module definition
+end+:: finish a class or module definition
+line+:: execute code on a new line
+raise+:: raise an exception
+return+:: return from a Ruby method

Tracing is disabled within the context of _proc_.

    class Test
    def test
      a = 1
      b = 2
    end
    end

    set_trace_func proc { |event, file, line, id, binding, classname|
       printf "%8s %s:%-2d %10s %8s\n", event, file, line, id, classname
    }
    t = Test.new
    t.test

      line prog.rb:11               false
    c-call prog.rb:11        new    Class
    c-call prog.rb:11 initialize   Object
  c-return prog.rb:11 initialize   Object
  c-return prog.rb:11        new    Class
      line prog.rb:12               false
      call prog.rb:2        test     Test
      line prog.rb:3        test     Test
      line prog.rb:4        test     Test
    return prog.rb:4        test     Test

请注意，对于 c-call 和 c-return 事件，返回的绑定是调用 C 方法的最近 Ruby 方法的绑定，因为 C 方法本身没有绑定。