从给定一个对象的对象

问题描述：

object_name = "hello"

有没有什么办法让变量的名称"object_name"？我需要创建一个带有变量名称和值的字符串，例如

"The name of the variable is 'object_name' and its value is 'hello'"

我想：

object_name.object_id 
# => 20084556

当然不是。 ... – sawa

...并希望永远不会;-) – Stefan

[从表示局部变量的字符串获取值]的可能重复（http://stackoverflow.com/questions/30840127/get-value-from-string-representing -local-variable） – mdesantis

答

我能想出的唯一办法是沿着这些路线的东西：

binding.local_variables.each do |var| 
    puts "The name of the variable is '#{var}' and its value is '#{eval(var.to_s)}'" 
    # or 
    # puts "The name of the variable is '#{var}' and its value is '#{binding.local_variable_get(var)}'" 
end 
# The name of the variable is 'object_name' and its value is 'hello'

当然会输出所有局部变量当前在范围，以及，eval。

你可以使用'binding.local_variable_get（“variable”）'而不是'eval' http://stackoverflow.com/a/30840502/584552 – mdesantis

答

def find_var(in_binding, object_id) 
    name = in_binding.local_variables.find do |name| 
    in_binding.local_variable_get(name).object_id == object_id 
    end 

    [name, in_binding.local_variable_get(name)] 
end 

the_answer = 42 
find_var binding, the_answer.object_id # => [:the_answer, 42] 

foo = 'bar' 
baz = [foo] 
find_var binding, baz.first.object_id # => [:foo, "bar"]

明显的垮台 - 指向同一个对象的两个变量。阿卡

a = b = 42

而不是使用'object_id'，你可以通过'equal？ – Stefan

@Stefan，你可以。 OP由于某种原因想要'object_id'。我不确定这可能会有什么用途。 – ndn

我明白了。我认为这是OP试图获得变量的名字。 – Stefan

答

只是出于好奇：

object_name = "hello" 
var_name = File.readlines(__FILE__)[__LINE__ - 2][/\w+(?=\s*=)/] 
puts "Variable named '#{var_name}' has value '#{eval(var_name)}'" 

> ruby /tmp/d.rb 
#⇒ Variable named 'object_name' has value 'hello'

答

我花了一段时间，但我解决了这个最终。感谢上述所有答案。以下是我用来解决问题的功能文件，步骤定义和方法。

Feature: try and work out a simple version of the f2d pages that could be used for all 

    Scenario Outline: first go 
    Given I set up an object for these things 
     | page_1 | page_2 | 
     | <page_1> | <page_2> | 
    Then I create objects and output two things for one 

    Examples: 
     | page_1 | page_2  | 
     | elephants | scary pants |

步骤定义：

Given(/^I set up an object for these things$/) do |table| 
    set_up_a_hash_from_a_table(table) 
end 

Then(/^I create objects and output two things for one$/) do 
    do_something_with_a_hash 
end

方法：

def set_up_a_hash_from_a_table(table) 
    @objects = Hash.new 
    @summary = Array.new 
    data = table.hashes 

    data.each do |field_data| 
    @objects['page_1'] = field_data['page_1'] 
    @objects['page_2'] = field_data['page_2'] 
    end 
end 

def do_something_with_a_hash 

    show_me_page_1 

    show_me_page_2 

    puts "Summary is #{@summary}" 

end 

def show_me_page_1 
    do_stuff_for_a_page('page_1') 
end 

def show_me_page_2 
    do_stuff_for_a_page('page_2') 
end 

def do_stuff_for_a_page(my_object) 
    puts "key is #{my_object} and value is #{@objects[my_object]}" 
    @summary.push("#{my_object} - #{@objects[my_object]}") 
    end

结果：

#=> key is page_1 and value is elephants 

#=> key is page_2 and value is scary pants 

#=> Summary is ["page_1 - elephants", "page_2 - scary pants"]

从给定一个对象的对象

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