你能回忆一下case case ruby​​中的一个方法吗？

时间：2016-04-08 04:48:40

标签： ruby

我想知道这是否可以在case语句中执行循环。如果响应（用户输入）输入错误，可以回忆一下该方法吗？还有更好的方法吗？

def game_type # Selecting humans or computers as players
    puts "Please select game type by number:"
    puts "1 - human vs human"
    puts "2 - computer vs computer"
    puts "3 - human vs computer"
    response = gets.chomp.to_i

    case response
    when 1
      puts "human vs human"
    when 2
      puts "computer vs computer"
    when 3
      puts "human vs computer"
    else
      game_type
    end
  end

3 个答案:

答案 0 :(得分：3)

递归调用方法是非常糟糕的事情，因为对于每个递归调用，会向调用堆栈添加一个额外的深度，并且您无法预测它的深度，从而降低性能。通常，应尽可能避免递归。在这种情况下，使用一个不需要递归调用的循环。

def game_type
  loop do
    puts <<~_
      Please select game type by number:
      1 - human vs human
      2 - computer vs computer
      3 - human vs computer
    _
    response = gets.to_i
    case response
    when 1
      puts "human vs human"
      break
    when 2
      puts "computer vs computer"
      break
    when 3
      puts "human vs computer"
      break
    end
  end
end

答案 1 :(得分：0)

此类交互的标准模式是有一个else分支，它会抱怨并将您送回另一个循环。

做Ruby时要记住的一件事是你应该尝试在常规结构中定义这样的东西，以避免大量的重复。 “不要重复自己”（DRY）原则非常重要。保持干燥！

所以在这种情况下：

GAME_TYPE_LIST = [
  "Human vs. Human",
  "Computer vs. Computer",
  "Human vs. Computer"
]

# Convert this list to a hash indexed by 1, 2, 3, etc.
GAME_TYPES = Hash[GAME_TYPE_LIST.each_with_index.map { |type, i| [ i + 1, type ] }]

这使得将来添加更多类型非常容易，而且还可以非常轻松地呈现您的菜单：

GAME_TYPES.each do |i, type|
  puts '%d - %s' % [ i, type ]
end

同样，当需要选择时：

game_type = nil

begin
  puts "Enter type:"

  game_type = gets.chomp.to_i
end while (!GAME_TYPES[game_type])

这将保持循环使用，你做对了。

答案 2 :(得分：-1)

  

我想知道这是否可以在case语句中执行循环。如果响应（用户输入）输入错误，可以回忆一下该方法吗？

虽然你可以这样做，正如sawa所说，出于性能原因，这不是Ruby的好习惯。

  

有更好的方法吗？

使用CUST_ID：

，而不是使用递归 
* What went wrong:
Execution failed for task ':app:packageDebug'.
> data        

* Try:        
Run with --info or --debug option to get more log output.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:packageDebug'.
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
        at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
        at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:64)
        at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
        at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:52)
        at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
        at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
        at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:203)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:185)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:62)
        at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:50)
        at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:25)
        at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:110)
        at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
        at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
        at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
        at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
        at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
        at org.gradle.initialization.DefaultGradleLauncher$4.run(DefaultGradleLauncher.java:154)
        at org.gradle.internal.Factories$1.create(Factories.java:22)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:52)
        at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:151)
        at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:32)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:99)
        at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:93)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:90)
        at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:62)
        at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:93)
        at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:82)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:94)
        at org.gradle.tooling.internal.provider.ExecuteBuildActionRunner.run(ExecuteBuildActionRunner.java:28)
        at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:43)
        at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:28)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:77)
        at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:47)
        at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:51)
        at org.gradle.launcher.exec.DaemonUsageSuggestingBuildActionExecuter.execute(DaemonUsageSuggestingBuildActionExecuter.java:28)
        at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:43)
        at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:170)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:237)
        at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:210)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:35)
        at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:24)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:206)
        at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:169)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
        at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
        at org.gradle.launcher.Main.doAction(Main.java:33)
        at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:54)
        at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:35)
        at org.gradle.launcher.GradleMain.main(GradleMain.java:23)
        at org.gradle.wrapper.BootstrapMainStarter.start(BootstrapMainStarter.java:30)
        at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:129)
        at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:61)
Caused by: java.lang.NoSuchFieldError: data
        at org.bouncycastle.cms.CMSProcessableByteArray.<init>(Unknown Source)
        at com.android.builder.signing.SignedJarBuilder.close(SignedJarBuilder.java:336)
        at com.android.builder.internal.packaging.Packager.sealApk(Packager.java:512)
        at com.android.builder.core.AndroidBuilder.packageApk(AndroidBuilder.java:1863)
        at com.android.build.gradle.tasks.PackageApplication.doFullTaskAction(PackageApplication.java:180)
        at com.android.build.gradle.internal.tasks.IncrementalTask.taskAction(IncrementalTask.java:98)
        at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.doExecute(AnnotationProcessingTaskFactory.java:244)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:220)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.execute(AnnotationProcessingTaskFactory.java:231)
        at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:209)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
        at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
        ... 60 more

（我还更改了你的代码以使用字典而不是loop语句，这使得代码比拥有一堆GAME_TYPES = { 1 => "human vs computer", 2 => "computer vs computer", 3 => "human vs human" } def game_type loop do puts <<~___ Please select game type by number: 1 - human vs human 2 - computer vs computer 3 - human vs computer ___ selection = gets.to_i if game_type_str = GAME_TYPES[selection] puts game_type_str break end end end 语句简洁得多。

相关问题
最新问题