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Io is a dynamic prototype-based programming language, first created by Steve Dekorte in 2002 for software development. It is purely object-oriented, inspired by Smalltalk, Self, Lua, Lisp, and Act1. Io’s unique feature is its consistency and simplicity, having a minimalistic syntax with less than a dozen different types of syntax, and only one data structure, the message. It supports actor-based concurrency, making it popular for high performance computing. References for this information can be found on the official Io language website (iolanguage.org) and Dekorte's personal blog.

Ask the right questions secure the right Io talent among an increasingly shrinking pool of talent.

First 20 minutes

General Io app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Io application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What are the basic data types in Io?

The basic data types in Io are Number, Boolean, List, String, and Object.

How would you create a new object in Io?

In Io, you can create a new object using the clone method. For example, 'Person := Object clone'.

What is the purpose of the 'slot' in Io?

In Io, a slot is a named location in an object where a value can be stored. Slots can contain any Io value such as a number, string, list, or another object.

How would you define a method in Io?

In Io, methods are defined by assigning a function to a slot. For example, 'Person greet := method("Hello" println)'.

What are the control flow structures in Io?

Io has several control flow structures including 'if', 'for', 'while', and 'switch'.

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What you’re looking for early on

Does the candidate demonstrate a strong understanding of Io programming language?

Has the candidate shown experience with concurrent programming?

Is the candidate able to solve problems and debug code effectively?

Does the candidate have experience with other programming languages?

Next 20 minutes

Specific Io development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you handle exceptions in Io?

In Io, exceptions can be handled using the 'catch' method. For example, 'try(message) catch(Exception)'.

Describe the difference between 'clone' and 'proto' in Io.

'Clone' creates a new object that shares the same slots as the original object. 'Proto' returns the prototype of an object, which is the object it was cloned from.

How would you implement inheritance in Io?

In Io, inheritance is implemented through the 'clone' method. When an object is cloned, it inherits the slots of the original object.

What is the role of the 'lobby' in Io?

The 'lobby' in Io is the global namespace. All objects are created in the lobby unless specified otherwise.

How would you perform file I/O in Io?

In Io, file I/O is performed using the 'File' object. For example, 'file := File with("filename.txt")'.

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At this point, a skilled Io engineer should demonstrate strong problem-solving abilities, proficiency in Io programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Io.

What does the following JSON code represent?
{
  'name': 'John',
  'age': 30,
  'city': 'New York'
}
The code represents a simple JSON object that contains three key-value pairs. The keys are 'name', 'age', and 'city', and their respective values are 'John', 30, and 'New York'.
What will be the output of the following JavaScript code that handles JSON?
let text = '{"name":"John", "age":30, "city":"New York"}';
let obj = JSON.parse(text);
console.log(obj.name);
The output of the code will be 'John'. The code first declares a JSON string, then it uses the JSON.parse() function to convert the string into a JavaScript object. Finally, it logs the 'name' property of the object to the console.
What does the following JavaScript code that handles JSON do?
let arr = '["Ford", "BMW", "Fiat"]';
let obj = JSON.parse(arr);
console.log(obj[1]);
The code first declares a JSON array of strings. It then uses JSON.parse() to convert the string into a JavaScript array. Finally, it logs the second element of the array (index 1) to the console. The output will be 'BMW'.
What does the following JavaScript code do with the JSON?
let text = '{"employees":[{"firstName":"John", "lastName":"Doe"},{"firstName":"Anna", "lastName":"Smith"},{"firstName":"Peter", "lastName":"Jones"}]}'
let obj = JSON.parse(text);
console.log(obj.employees[1].firstName);
The code first declares a JSON string that contains an array of objects. Each object represents an employee with a 'firstName' and 'lastName'. Then, it uses JSON.parse() to convert the string into a JavaScript object. Finally, it logs the 'firstName' of the second employee in the array to the console. The output will be 'Anna'.

Wrap-up questions

Final candidate for Io Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Io application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

Describe the difference between ':=', '=', and '::=' in Io.

':=' is used to create a new slot and assign a value to it. '=' is used to assign a value to an existing slot. '::=' is used to create a slot and assign a value to it, but also updates the slot in the object's prototype if it exists.

How would you create a list in Io and add elements to it?

In Io, a list is created using the 'list' method and elements are added using the 'append' method. For example, 'myList := List clone; myList append(1)'.

What are coroutines in Io and how would you use them?

Coroutines in Io are a way to perform non-blocking operations. They are created using the 'Coroutine' object and executed with the 'resume' method.

Io application related

Product Perfect's Io development capabilities

Beyond hiring for your Io engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Io projects, and can engage in multiple capacities.

Io Consultive assessments

Io Application Conversion Assessment Io Application Integration Assessment Io Data & Database Integration Assessment

Custom Io development projects

Custom Io App Conversion Io Custom App Development Process App UI Design for Io Facelifts

Hiring guide for Io Engineers

Io Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Io engineer at this point.

Io Consultive assessments

Custom Io development projects