The latest 2023 advanced level Ruby interview questions, including answers. A must for brushing up on questions! Record it.
The latest 2023 advanced level Ruby interview questions, including answers. A must for brushing up on questions! Record it.
A good memory is not as good as a bad pen
The content comes from the Interview Guide - Collection of Advanced Difficulty Ruby Interview Questions
Question: In Ruby, how to use C API to extend Ruby's functionality? Please give an example.
In Ruby, Ruby functionality can be extended through the C API. Writing Ruby extensions using the C API enables high-performance code and allows you to take advantage of the power and flexibility of the C language.
The following is a simple example that shows how to use the C API to create a HelloRuby module called Ruby that contains a method hellothat returns a string "Hello World!":
- Create a header file :
Create ahello.hheader file named , which contains your extension definitions.
#ifndef HELLO_H
#define HELLO_H
#include <[ruby](/search?q=ruby).h>
void Init_hello();
#endif /* HELLO_H */
- Create a source file :
Create ahello.csource file named , which contains your extension implementation.
#include "hello.h"
VALUE method_hello(VALUE self) {
return rb_str_new_cstr("Hello World!");
}
void Init_hello() {
VALUE mHello = rb_define_module("Hello");
rb_define_method(mHello, "hello", method_hello, 0);
}
- Compile extension :
Usegcca compiler to compile source files into dynamic link libraries (.soor DLLs.dll).
For Linux and macOS:
gcc -shared -o hello.so -fPIC hello.c -I/usr/local/include/ruby-3.1.0 -L/usr/local/lib -lruby
For Windows:
gcc -shared -o hello.dll -Ic:\Ruby31-x64\include -Lc:\Ruby31-x64\lib hello.c -lmsvcrt-ruby310
- Loading extensions in Ruby :
In Ruby code, userequirestatements to load your extensions.
require 'hello'
puts Hello.hello # 输出: Hello World!
In this example, we first define a C function method_hellothat accepts a Ruby object as a parameter (in this case self) and returns a Ruby object representing a string. Then we Init_helloregistered this method in the function, making it Hellopart of the module.
In the above way, you can use the C API to extend Ruby's functionality. In actual development, you may need to handle more complex logic, such as processing Ruby objects, accessing and modifying memory, etc. In order to simplify these operations, you can use some tool libraries, such as Rice, FFI, etc.
Q: How to use TracePoint API for code tracing and analysis in Ruby? Please give an example.
Ruby's TracePoint API provides a powerful way to trace code execution, including events such as calls, thread starts and ends, exceptions thrown and caught. This enables developers to gain insight into a program's behavior and perform debugging, performance analysis, or code generation.
The following is an example of how to use the TracePoint API for code tracing and analysis:
- First, we need to create a new TracePoint object and specify the events we want to listen for. We can listen to various types of events, such as method invocation (
:call), method return (:return), line execution (:line), etc.
# 在这里处理跟踪事件
end
- Next, we can enable this tracking point to start listening for specified events.
- Now, any matching event that occurs in our code will trigger the block we defined in the TracePoint object. In this block, we can access various information about the event, such as the method name that triggered the event, file name, line number, etc.
puts "Called #{tp.method_id} at line #{tp.lineno} in #{tp.path}"
end
trace.enable
def example_method
puts 'Hello, world!'
end
example_method
- TracePoint can be disabled when we no longer need tracing.
- For a more comprehensive tracing experience, we can combine multiple event types together or create separate TracePoint objects for each event type.
puts "Called #{tp.method_id} at line #{tp.lineno} in #{tp.path}"
end
trace_returns = TracePoint.new(:return) do |tp|
puts "Returned from #{tp.method_id} at line #{tp.lineno} in #{tp.path}"
end
trace_calls.enable
trace_returns.enable
def example_method
puts 'Hello, world!'
end
example_method
trace_calls.disable
trace_returns.disable
In this way, we can easily trace code execution and obtain detailed event information, which is very useful for debugging, performance optimization, and understanding how the code works.
Question: In Ruby, how to use the FFI library to call C language functions? Please give an example.
In Ruby, the FFI (Foreign Function Interface) library allows you to directly call C language functions, thus extending Ruby's capabilities. The following is a simple example showing how to use the FFI library to call a helloC function named:
- Create a C source file :
Create ahello.csource file named , which contains your C function.
#include <stdio.h>
void hello() {
printf("Hello World!\n");
}
- 编译C代码 ：
使用gcc编译器将源文件编译为动态链接库（.so或.dll）。
对于Linux和macOS：
gcc -shared -o libhello.so hello.c
对于Windows：
gcc -shared -o hello.dll hello.c
- 编写Ruby代码 ：
在Ruby代码中，使用FFI库加载动态链接库，并定义C函数。
require 'ffi'
module Hello
extend FFI::Library
ffi_lib './libhello.so' # 对于Linux和macOS
# ffi_lib 'hello.dll' # 对于Windows
attach_function :hello, [], :void
end
Hello.hello # 输出: Hello World!
在这个例子中，我们首先使用FFI::Library模块的ffi_lib方法指定要加载的动态链接库。然后，我们使用attach_function方法定 义了一个新的Ruby方法hello，它对应于我们的C函数。这个新定义的方法没有参数，并且返回值类型为void。
通过以上方式，你就能够使用FFI库来调用C语言函数了。实际开发中，可能需要处理更复杂的逻辑，例如处理不同类型的参数、访问和修改内存等。为了简化这些操作，你可以查阅FFI库的文档，了解其提供的各种工具和功能。
问: 在Ruby中，如何使用JRuby来在JVM上运行Ruby代码？请举例说明。
JRuby是一个用于在Java虚拟机（JVM）上运行Ruby代码的开源实现。它允许开发者利用Java平台的强大功能和生态系统，同时保持Ruby语言的简洁性和表达力。以下是如何使用JRuby来在JVM上运行Ruby代码的步骤：
- 安装JRuby：首先，你需要在你的系统上安装JRuby。你可以从JRuby的官方网站下载并按照说明进行安装。或者，如果你使用的是包管理器（如Homebrew），可以使用以下命令：
- 编写Ruby代码：就像使用其他Ruby解释器一样，你可以在文本编辑器中编写Ruby代码。
puts 'Hello, world!'
- 使用JRuby执行代码：一旦你有了一个Ruby脚本，你可以使用
jruby命令来执行它。
- 与Java交互：JRuby的一个重要特性是它能够无缝地与Java代码交互。这意味着你可以调用Java库，创建Java对象，并将Ruby对象转换为Java对象。例如，你可以像这样在Ruby代码中导入和使用Java类：
java_import 'java.util.ArrayList'
list = ArrayList.new
list.add('Hello')
list.add('world')
puts list.to_s
- 将Ruby代码打包成jar文件：JRuby还允许你将Ruby代码打包成Java jar文件，这使得你可以像部署Java应用一样部署Ruby应用。要创建一个包含Ruby代码的jar文件，你可以使用
warble jar命令（需要先安装Warbler gem）。
- 在Java应用程序中使用JRuby：如果你想在Java应用程序中使用Ruby代码，你可以使用JRuby的
ScriptingContainer类。这是一个简单的例子：
public class JRubyExample {
public static void main(String[] args) {
ScriptingContainer container = new ScriptingContainer();
container.runScriptlet("puts 'Hello, world!'");
}
}
通过这些步骤，你可以在JVM上运行Ruby代码，并充分利用Java平台的功能。
问: 在Ruby中，如何使用RubyVM API来操作Ruby虚拟机的内部状态？请举例说明。
在Ruby中，RubyVM类提供了许多方法来操作Ruby虚拟机（VM）的内部状态。这些方法允许开发者深入到VM的底层，并进行一些高级的调试、性能分析和优化。
以下是一些使用RubyVM API的例子：
- 获取当前正在运行的线程列表：
puts RubyVM::Thread.list
- 检查一个对象是否为Ruby VM中的Fixnum类型：
puts RubyVM::Type.object_type(42) == :integer
- 查看某个方法的字节码：
def add(a, b)
a + b
end
RubyVM::InstructionSequence.disasm(add)
- 使用trace_point观察方法调用：
tp = TracePoint.new(:call) do |t|
puts "Called: #{t.method_id}"
end
tp.enable
add(1, 2)
tp.disable
- 调整VM的全局堆大小：
RubyVM::GC.set_heap_total(100 * 1024 * 1024) # 设置总堆大小为100MB
RubyVM::GC.set_heap_free_min(10 * 1024 * 1024) # 设 置最小空闲空间为10MB
- 访问编译后的指令集（Instruction Sequence，IS）：
code = <<-RUBY
def hello(name)
puts "Hello, #{name}!"
end
RUBY
iseq = RubyVM::InstructionSequence.compile(code)
puts iseq.disasm # 输出编译后的指令集
hello("World") # 执行定义的方法
请注意，直接操作Ruby VM的内部状态可能会影响程序的稳定性和性能。除非你非常清楚自己在做什么，否则建议避免这样做。这些API主要用于调试、性能分析和理解Ruby解释器的行为。
问: 在Ruby中，如何使用Ractor库来实现并发执行和消息传递？请举例说明。
Ractor是Ruby 3引入的一种并发模型，它基于Actor模型，并通过消息传递来实现并行性和线程安全性。以下是使用Ractor库来实现并发执行和消息传递的步骤：
-
首先，确保你的Ruby版本至少为3.0，因为Ractor是从这个版本开始引 入的。
-
创建一个Ractor：要创建一个新的Ractor，你需要定义一个接收和处理消息的方法。在这个方法中，你可以执行任何你想要的代码，只要它是线程安全的。以下是一个简单的例子：
ractor = Ractor.new do
loop do
message = Ractor.receive
puts "Received message: #{message}"
end
end
ractor.take # 这会阻塞，直到有消息被发送给ractor
- 向Ractor发送消息：你可以使用
Ractor.send或Ractor#send方法向Ractor发送消息。当Ractor收到消息时，它会调用你在创建Ractor时定义的方法来处理这些消息。
- 创建多个Ractor：你可以创建多个Ractor来实现并行执行。每个Ractor都在自己的独立上下文中运行，因此它们可以安全地并行执行而不会互相干扰。
ractor2 = Ractor.new { ... }
ractor1.send('Message for ractor1')
ractor2.send('Message for ractor2')
- 使用Ractor之间的通信：Ractor可以通过发送和接收消息来进行通信。你可以创建一个Ractor网络，其中不同的Ractor负责不同的任务，并通过消息传递来协调他们的工作。
while true
number = Ractor.receive
Ractor.yield
Ractor.send(number * number)
end
end
worker_ractor = Ractor.new(result_ractor) do |result|
loop do
number = Ractor.receive
squared = result.take
puts "The square of #{number} is #{squared}"
end
end
worker_ractor.send(5)
在这个例子中，我们创建了两个Ractor：一个计算平方（result_ractor），另一个显示结果（worker_ractor）。这两个Ractor通过消息传递进行通信。
- 资源隔离：Ractor之间共享数据是不安全的，除非明确指定。Ractor提供了一种机制来安全地共享对象，即使用关键字
share声明变量或对象。
shared_array.share
ractor1 = Ractor.new(shared_array) do |array|
array << 4
end
ractor1.take
p shared_array # => [1, 2, 3, 4]
在上面的例子中，我们创建了一个冻结的数组并通过share关键字将其标记为可共享。然后，我们可以在不同的Ractor中修改这个数组，而不用担心数据竞争问题。
通过以上示例，你可以看到如何使用Ractor库在Ruby中实现并发执行和消息传递。Ractor提供了一种简单、安全的方式来编写并行代码，使得开发者能够更好地利用多核处理器的优势。
问: 在Ruby中，如何使用Inline C来直接在Ruby代码中嵌入C代码？请举例说明。
在Ruby 中，你可以使用RubyInline gem来直接在Ruby代码中嵌入C代码。RubyInline是一个允许你在Ruby代码中内联编译和执行C、Java或.NET（通过IronRuby）的库。它简化了与C语言的交互，并且对于需要高性能的特定部分代码非常有用。
以下是一个简单的例子，展示了如何使用RubyInline在Ruby代码中嵌入C代码：
首先，确保已经安装了RubyInline gem：
gem install RubyInline
然后，在你的Ruby脚本中引入inline模块并定义一个类，在其中包含inlinedo块。在这个块内部，可以编写C代码并调用builder.c方法将其添加到编译后的函数中：
require 'inline'
class MyMath
inline do |builder|
builder.c <<-EOS
double square(double x) {
return x * x;
}
EOS
end
end
puts MyMath.new.square(5.0) # 输出25.0
在这个例子中，我们创建了一个名为MyMath的类，并在其内部定义了一个名为square的C函数，该函数接受一个浮点数作为参数并返回其平方。然后，我们可以在Ruby代码中像调用普通Ruby方法一样调用这个C函数。
Note: Although RubyInlineit makes it easier to embed C code in Ruby code, this does not mean that you should randomly mix C code into Ruby code. Doing so may cause readability and maintainability issues, and in some cases may impact performance. You should consider this approach only if you are sure you need to take advantage of C's performance advantages.
Q: In Ruby, how to use the Ruby Prof library for performance analysis and tuning? Please give an example.
Ruby Prof is a library for analyzing the performance of Ruby code. It can provide detailed information about code execution time, memory usage, etc., helping developers identify bottlenecks in the program and optimize them. Here are the steps on how to use the Ruby Prof library for performance analysis and tuning:
- Install Ruby Prof: First, you need to install the Ruby Prof gem. Run the following command in your project directory:
- Preparing the code for analysis: To demonstrate how to use Ruby Prof, we create a simple example that contains a method to calculate the Fibonacci sequence.
def fibonacci(n)
return n if n <= 1
fibonacci(n - 1) + fibonacci(n - 2)
end
puts fibonacci(30)
- Analyzing code using Ruby Prof: Now we can use Ruby Prof to analyze
fibonaccithe performance of a method. We will useRubyProf.profilea method to capture performance data when this method is executed and output it to a file.
result = RubyProf.profile do
Fibonacci.new.fibonacci(30)
end
printer = RubyProf::FlatPrinter.new(result)
printer.print(File.open('profile.txt', 'w'))
-
View analysis results: After the analysis is complete, you can view the generated
profile.txtfiles for a performance report. This report will display information such as the number of executions of each method, the total time, and the since time (excluding the time of sub-methods). -
Optimize based on reports: Based on the information provided by reports, you can identify which methods or code segments are performance bottlenecks and optimize them. For example, in the Fibonacci sequence example above, we might notice that the recursive implementation is very inefficient and consider using iteration or other algorithms to improve performance.
-
Use other types of printers: Ruby Prof provides a variety of different printers that can help you view performance data in different formats. For example, you can use
RubyProf::GraphHtmlPrinterto export data to HTML format for easier visualization.
printer.print(File.open('profile.html', 'w'))
Through these steps, you can use the Ruby Prof library to analyze the performance of Ruby code and make optimizations based on the analysis results. This helps you write more efficient and faster code.
Question: In Ruby, how to use Refinements to locally modify and extend the behavior of a class? Please give an example.
In Ruby, Refinements (also called local scopes of module mixins) allow you to modify or extend the behavior of a class in a local scope without affecting the global namespace. This helps avoid side effects and potential conflicts on a global scale.
Here is an example using Refinements:
# 假设我们有一个已有的类，我们想要在其上添加一个方法。
class String
def to_uppercase
upcase
end
end
# 使用refinements，我们可以创建一个新的方法，但只在特定的作用域内生效。
module StringExtensions
refine String do
def to_uppercase
downcase # 这 里我们改变了to_uppercase的行为
end
end
end
# 在这个模块作用域之外，String的to_uppercase方法仍然是原始行为。
puts "hello".to_uppercase # 输出HELLO
# 然后我们可以使用using关键字将这个模块引入作用域。
using StringExtensions
# 在这个作用域内，String的to_uppercase方法被修改为新的行为。
puts "hello".to_uppercase # 输出hello
# 一旦离开using的作用域，原始的行为就会恢复。
puts "hello".to_uppercase # 输出HELLO
In this example, we first define a StringExtensionsmodule called , which contains a refinement that overrides Stringthe class's to_uppercasemethods. Then, we use usingthe keyword to introduce this module into our scope, so that within this scope, Stringthe class's to_uppercasemethods will change its behavior. Once out of this scope, the original to_uppercasemethod behavior is restored.
Note: One limitation of Refinements is that they cannot be used in top-level code or when loading other files. Therefore, they are best used inside methods or in local scopes such as loops.
Q: In Ruby, how can you use the Sorbet static type checker to improve code quality and maintainability? Please give an example.
Sorbet is a static type checker developed by Stripe for the Ruby language. It provides a way to add type annotations to Ruby code and detect potential type errors at compile time. By using Sorbet, developers can improve code quality and maintainability, reduce runtime errors, and make code easier to understand and maintain.
Here are the steps on how to use the Sorbet static type checker to improve code quality and maintainability:
- Install Sorbet: First, you need to install the Sorbet gem. Run the following command in your project directory:
- Initialize Sorbet: In order to use Sorbet in your project, you need to run
srb initthe command. This will automatically create the necessary configuration files and directory structure for you.
- Add type annotations: Next, you can start adding type annotations to your code. These annotations tell Sorbet information about the expected types of variables, parameters, and return values. Sorbet supports a variety of types, including basic types (such as
Integer,Stringetc.), custom classes and modules, tuple types, and more complex generic and constrained types.
class Greeter
extend T::Sig
sig { params(name: String).returns(String) }
def greet(name)
"Hello, #{name}!"
end
end
puts Greeter.new.greet("World")
- Run type checking: You can use
srb tcthe command to run type checking. If Sorbet detects any type of error, it displays a detailed report indicating which code segments are problematic.
-
Incremental type checking with Sorbet: For large projects, you may want to type check only modified files to speed things up. For this you can use
srb tc --incrementalthe command. -
Gradually migrate your existing codebase: If you are introducing Sorbet to your existing Ruby codebase, it is best to do it in stages. First, you can start with the core and most important part, and then gradually expand to other parts. This helps you better manage the migration process and ensures that code quality is maintained throughout the process.
-
Use the VS Code Sorbet extension: For a better integrated development environment (IDE) experience, you can install the Sorbet extension for VS Code. This will provide you with code completion, error prompts, and other useful features.
With these steps, you can use the Sorbet static type checker to improve the quality and maintainability of your Ruby code. While it may take some getting used to and adding type annotations at first, over time you'll find that this process helps avoid many potential mistakes and makes collaboration between teams smoother.