Question

我可以创建一个哈希数组：

people = [
  {"Name" => "J.R. Kruger", "State" => "WA"},
  {"Name" => "Carl Hennings", "State" => "CA"}
]

然后我可以使用each声明：

people.each { |p| puts p["Name"] }

它将按照我的预期呈现一个名单列表。

"J.R. Kruger"
"Carl Hennings"

但是，如果我使用的JSON对象的Web服务被解析为一个哈希数组：

speakers = JSON.parse(open("http://some.url.com/speakers.json").read)

它返回了一系列哈希值。但是，如果我尝试和上面代表人物的哈希数组做同样的事情：

speakers.each {|s| puts s["SpeakerName"]}

它只会输出扬声器的全部内容，这是一个散列数组，而不是数组中每个散列的"SpeakerName"键值的预期列表。

我应该补充说我能做到：

speakers[0]["SpeakerName"]

并获得所需的结果，以确保它不是错误的密钥。

缺少什么？

更新：

从文件输出：

[
  {
    "Title"=>"Working with Maps in iOS 6: MapKit and CoreLocation in Depth",
    "Abstract"=>"Adding a Map to an App and recording a User\u2019s location as they use the App has become a common must have feature in may of todays popular applications. This presentation will go over the updated iOS 6 APIs for accomplishing such tasks including map annotations, dragging and dropping custom pins as well as delve into some of the finer aspects of the required location based calculations one needs to consider to find the center of the map or the distance between two points. Additionally the presentation will go over techniques to update a MapView with a moving object as well as positioning the image for the object properly along its heading. This will be a straight forward hands on development presentation with plenty of code examples.",
    "Start"=>"2013-01-11T20:35:00Z",
    "Room"=>"Salon A",
    "Difficulty"=>"Intermediate",
    "SpeakerName"=>"Geoffrey Goetz",
    "Technology"=>"Mac/iPhone",
    "URI"=>"/api/sessions.json/Working-with-Maps-in-iOS-6-MapKit-and-CoreLocation-in-Depth",
    "EventType"=>"Session",
    "Id"=>"4f248d87-0e18-488d-8cef-5e4130b8bb20",
    "SessionLookupId"=>"Working-with-Maps-in-iOS-6-MapKit-and-CoreLocation-in-Depth",
    "SpeakerURI"=>"/api/speakers.json/Geoffrey-Goetz"
  },
  {
    "Title"=>"Vendor Sessions - Friday",
    "Start"=>"2013-01-11T20:00:00Z",
    "End"=>"2013-01-11T20:20:00Z",
    "Room"=>"TBD",
    "Difficulty"=>"Beginner",
    "SpeakerName"=>"All Attendees",
    "Technology"=>"Other",
    "URI"=>"/api/sessions.json/Vendor-Sessions--Friday",
    "EventType"=>"Session",
    "Id"=>"43720cb8-d8ca-4694-8806-debcbdefa239",
    "SessionLookupId"=>"Vendor-Sessions--Friday",
    "SpeakerURI"=>"/api/speakers.json/All-Attendees"
  },
  {
    "Title"=>"Vendor Sessions - Thursday",
    "Start"=>"2013-01-10T20:00:00Z",
    "End"=>"2013-01-10T20:20:00Z",
    "Room"=>"TBD",
    "Difficulty"=>"Beginner",
    "SpeakerName"=>"All Attendees",
    "Technology"=>"Other",
    "URI"=>"/api/sessions.json/Vendor-Sessions--Thursday",
    "EventType"=>"Session",
    "Id"=>"2df202e4-219c-4efb-a838-3898d183dd19",
    "SessionLookupId"=>"Vendor-Sessions--Thursday",
    "SpeakerURI"=>"/api/speakers.json/All-Attendees"
  },
  {
    "Title"=>"Version your database on nearly any platform with Liquibase",
    "Abstract"=>"If you are still writing one-off scripts to manage your database, then it is time to make your life much simpler and less error-prone.  \nWe'll spend the time discussing Liquibase, a tool that will help you to manage that process.  It will even allow you to check your schema and seed data into source-control, and get new environments up and running quickly.  This session will focus not on the merits of using such a tool, but on its workflow and implementation in a project.  We'll run through the majority of features from the command-line, demonstrating that as long as a Java Runtime Environment (jre) is available, Liquibase can be used during deployments on any platform.  We'll also touch on usage with maven and quirks of Liquibase that are good to know ahead of time.",
    "Start"=>"2013-01-11T20:35:00Z",
    "Room"=>"Sagewood/Zebrawood",
    "Difficulty"=>"Beginner",
    "SpeakerName"=>"Daniel Bower",
    "Technology"=>"Continuous Deployment",
    "URI"=>"/api/sessions.json/Version-your-database-on-nearly-any-platform-with-Liquibase",
    "EventType"=>"Session",
    "Id"=>"4abb3869-bacd-42e1-93dc-14e712090b65",
    "SessionLookupId"=>"Version-your-database-on-nearly-any-platform-with-Liquibase",
    "SpeakerURI"=>"/api/speakers.json/Daniel-Bower"
  }
]

Answer 1

我认为您正在使用IRB或Pry来查看您的数据和代码，这是正确的做法，但由于环境的行为方式，它也可能令人困惑。

我正在使用Pry，如果我查看你的数组，并从每个哈希中提取'SpeakerName'字段，我看到有四个返回：

[9] (pry) main: 0> ary.map{ |h| h['SpeakerName'] }
[
    [0] "Geoffrey Goetz",
    [1] "All Attendees",
    [2] "All Attendees",
    [3] "Daniel Bower"
]

如果我使用each并遍历数组，我会看到四个名称输出，然后是每个名称的返回值，然后显示Pry。我在这里截断了它，因为它太长了。

[10] (pry) main: 0> ary.each{ |h| puts h['SpeakerName'] }
Geoffrey Goetz
All Attendees
All Attendees
Daniel Bower
[
[0] {
              "Title" => "Working with Maps in iOS 6: MapKit and CoreLocation in Depth",...

要显示它是返回值，我通过将;nil附加到该行来欺骗Pry使用不同的返回值：

[11] (pry) main: 0> ary.each{ |h| puts h['SpeakerName'] };nil
Geoffrey Goetz
All Attendees
All Attendees
Daniel Bower
nil

在输出名字后，Pry尽职尽责地返回nil。

此问题仅发生在IRB或Pry中，而不是在正在运行的程序中。

Answer 2

答案实际上证明是我在OP中建议的 - ＆gt;结果是Array＃每个都返回数组。

因此，当在一个实例变量上调用它时，它会在说（视图）中发布相同的结果，它会在执行块后返回整个数组。

请参阅Ruby Api docs了解源代码以及它如何返回最终返回结果的数组。

什么＆＃34;每个＆＃34;方法呢？

2 个答案: