为什么#{}没有将值添加到字符串中？

Question

使用httparty我正在发出GET请求:

https://api.marktplaats.nl/api3/categories.json?oauth_token=1me6jq76h8t6rim747m7bketkd&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0

代码A:

require 'httparty'

class Marktplaats  
  def categories
    HTTParty.get('https://api.marktplaats.nl/api3/categories.json?oauth_token=1me6jq76h8t6rim747m7bketkd&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0')
  end
end

代码B:

require 'httparty'

class Marktplaats
  @oauth_token = '1me6jq76h8t6rim747m7bketkd'

  def categories
    HTTParty.get("https://api.marktplaats.nl/api3/categories.json?oauth_token=#{@oauth_token}&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0")
  end
end

做的时候:

m = Marktplaats.new
m.categories

代码A有效,但代码B没有.

调用.request.last_uri.to_s代码B的GET调用返回:

https://api.marktplaats.nl/api3/categories.json?oauth_token=&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0

怎么可能出错？

Answer 1

这是在类级别与实例级别定义变量的情况.您已@oauth_token在类级别定义,但尝试在实例级别使用它,但不能.尝试将代码更改为:

class Marktplaats
  def initialize
    @oauth_token = '1me6jq76h8t6rim747m7bketkd'
  end

  def categories
    HTTParty.get("https://api.marktplaats.nl/api3/categories.json?oauth_token=#{@oauth_token}&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0")
  end
end

或者对此,它使用在类和实例级别都可访问的常量(但不应该更改):

class Marktplaats
  OAUTH_TOKEN = '1me6jq76h8t6rim747m7bketkd'

  def categories
    HTTParty.get("https://api.marktplaats.nl/api3/categories.json?oauth_token=#{OAUTH_TOKEN}&api_ver=3.7&session=ebc565b8-659f-40f6-9d0a-96986f1d1595&screenWidth=62&screenHeight=111&app_ver=Android3.1.0")
  end
end