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instance method

Binding#eval

(::string src, ?::string filename, ?::int lineno) -> untyped

binding.eval(string, filename = default_filename, lineno = 1) → obj

static VALUE
bind_eval(int argc, VALUE *argv, VALUE bindval)
{
    VALUE args[4];

    rb_scan_args(argc, argv, "12", &args[0], &args[2], &args[3]);
    args[1] = bindval;
    return rb_f_eval(argc+1, args, Qnil /* self will be searched in eval */);
}

Evaluates the Ruby expression(s) in string in the context of self. Returns the result of the last expression:

Example

def get_binding(param) = binding
b = get_binding("hello")
b.eval("param")   #=> "hello"

If the optional filename is given, it will be used as the filename of the evaluation (for __FILE__ and errors). Otherwise, it will default to (eval at __FILE__:__LINE__) where __FILE__ and __LINE__ are the filename and line number of the caller, respectively:

Example

b.eval("puts __FILE__") # => "(eval at test.rb:4)"
b.eval("puts __FILE__", "foobar.rb") # => "foobar.rb"

If the optional lineno is given, it will be used as the line number of the evaluation (for __LINE__ and errors). Otherwise, it will default to 1:

Example

b.eval("puts __LINE__") # => 1
b.eval("puts __LINE__", "foobar.rb", 10) # => 10

Ruby version changes

3.0
- Binding#eval when called with one argument will use “(eval)” for __FILE__ and 1 for __LINE__ in the evaluated code. [Bug #4352] [Bug #17419]

See also #implicit_parameter_defined? #implicit_parameter_get also in 4.0 · 3.4 · 3.3 · 3.2 · 3.1 · 3.0

next ›#implicit_parameter_defined?