ios - 使用 RubyMotion 解析 JSON

Question

我有一个 RubyMotion 类，它从 Twitter 的搜索 API 读取数据来创建 Tweet 对象，如下所示。

当我运行它时，我收到此错误:

(main)> 2012-11-08 17:01:32.634 Hello[39940:c07] -[__NSCFString bytes]: unrecognized selector sent to instance 0xea1f800
2012-11-08 17:01:32.685 Hello[39940:c07] json.rb:20:in `parse:': NSInvalidArgumentException: -[__NSCFString bytes]: unrecognized selector sent to instance 0xea1f800 (RuntimeError)
    from tweets_controller.rb:11:in `create_tweets'
    from tweets_controller.rb:7:in `tweets'
    from twitter_view_controller.rb:21:in `tableView:numberOfRowsInSection:'
    from app_delegate.rb:10:in `application:didFinishLaunchingWithOptions:'
2012-11-08 17:01:32.686 Hello[39940:c07] *** Terminating app due to uncaught exception 'RuntimeError', reason: 'json.rb:20:in `parse:': NSInvalidArgumentException: -[__NSCFString bytes]: unrecognized selector sent to instance 0xea1f800 (RuntimeError)
    from tweets_controller.rb:11:in `create_tweets'
    from tweets_controller.rb:7:in `tweets'
    from twitter_view_controller.rb:21:in `tableView:numberOfRowsInSection:'
    from app_delegate.rb:10:in `application:didFinishLaunchingWithOptions:'

我应该如何解析 JSON？

class TweetsController
  def initialize
    @twitter_accounts = %w(dhh google)
  end

  def tweets
    @tweets ||= create_tweets
  end

  def create_tweets
    BW::JSON.parse(twitter_search_results)["results"].each do |result|
      @tweets << Tweet.new(result)
    end
    @tweets
  end

  def twitter_search_results
    query = @twitter_accounts.map{ |account| "from:#{account}" }.join(" OR ")
    url_string = "http://search.twitter.com/search.json?q=#{query}"
    url_string_escaped = url_string.stringByAddingPercentEscapesUsingEncoding(NSUTF8StringEncoding)
    url = NSURL.URLWithString(url_string_escaped)
    request = NSURLRequest.requestWithURL(url)
    response = nil
    error = nil
    data = NSURLConnection.sendSynchronousRequest(request, returningResponse: response, error: error)
    ##raise "BOOM!" unless (data.length > 0 && error.nil?)
    json = NSString.alloc.initWithData(data, encoding: NSUTF8StringEncoding)
  end
end

class Tweet
  attr_reader :created_at, :from_user, :text
  def initialize(tweet_result)
    @created_at = tweet_result["created_at"]
    @from_user = tweet_result["from_user"]
    @text = tweet_result["text"]
  end
end

Answer 1

有几个 CocoaPods 可以解决这个问题。特别是 JSONKit。

编辑:这不是气泡包装错误。这是一个如何解读 Twitter 回应的问题。我有一个使用 bubblewrap 和 JSONKit 执行此操作的示例。我很快就会把它放到 GitHub 上。简而言之，Twitter 返回一个数组的数组。第一个元素是该组中的内容，第二个元素是实际数据。您想要迭代最外层的数组，查找第一个元素是结果的数组，然后使用第二个元素导出响应数据。以下是两种替代实现:

def create_tweets_using_bubblewrap
  @twitter_accounts = %w(dhh google)
  query = @twitter_accounts.map{ |account| "from:#{account}" }.join(" OR ")
  url_string = "http://search.twitter.com/search.json?q=#{query}"

  BW::HTTP.get(url_string) do |response|
    parsed = BW::JSON.parse response.body.to_str
    parsed.each do |item|
      next if item[0] != 'results'
      @feed = []
      item[1].each do |tweet|
        @feed << {:from => tweet['from_user'], :text => tweet['text']}
      end
    end
  end
  @feed
end

def create_tweets_using_jsonkit
  @twitter_accounts = %w(dhh google)
  query = @twitter_accounts.map{ |account| "from:#{account}" }.join(" OR ")
  url_string = "http://search.twitter.com/search.json?q=#{query}"

  error_ptr = Pointer.new(:object)
  BW::HTTP.get(url_string) do |response|
    parsed = response.body.to_str.objectFromJSONStringWithParseOptions JKParseOptionValidFlags, error: error_ptr
    if parsed.nil?
      error = error_ptr[0]
      puts error.userInfo[NSLocalizedDescriptionKey]
      @timer.setValid false
    else
      parsed.each do |item|
        next if item[0] != 'results'
        @feed = []
        item[1].each do |tweet|
          @feed << {:from => tweet['from_user'], :text => tweet['text']}
        end
      end
    end
  end
  @feed
end 

http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSJSONSerialization_Class/Reference/Reference.html