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Delphi is a high-level, compiled, strongly typed language that supports structured and object-oriented design. Developed by Borland in 1995, it was originally based on the Pascal programming language and designed for rapid application development. Delphi's integrated development environment (IDE) provides a visual approach to creating Windows applications, combining the ease of visual component-oriented development with the precision of the Pascal programming language. Today, Delphi is managed by Embarcadero Technologies and used worldwide for creating a wide range of applications across multiple platforms. Notably, Delphi was instrumental in developing Skype before it was acquired by Microsoft.

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

First 20 minutes

General Delphi app knowledge and experience

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

How would you declare a variable in Delphi?

You can declare a variable in Delphi using the 'var' keyword followed by the variable name and its type. For example, 'var x: Integer;' declares an integer variable named x.

What are the basic data types in Delphi?

The basic data types in Delphi include Integer, Real, Char, String, Boolean, Byte, and Variant.

Describe the difference between a procedure and a function in Delphi.

In Delphi, both procedures and functions are used to encapsulate a series of commands. The main difference is that a function returns a value while a procedure does not.

How would you handle exceptions in Delphi?

In Delphi, you can handle exceptions using the try-except block. Any code that may raise an exception is placed within the 'try' block, and the code to handle the exception is placed within the 'except' block.

What is the use of the 'with' statement in Delphi?

The 'with' statement in Delphi is used to simplify the code when you need to reference the same object or record multiple times. It allows you to write the object or record name once instead of repeating it for every property or method you want to access.

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What you’re looking for early on

Does the candidate have a strong understanding of Delphi language?

Can the candidate solve complex problems using Delphi?

How well does the candidate understand and apply object-oriented programming concepts?

Is the candidate familiar with the latest versions of Delphi?

Next 20 minutes

Specific Delphi 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 create a class in Delphi?

In Delphi, you can create a class using the 'type' keyword followed by the class name and the keyword 'class'. The properties and methods of the class are then declared within the class declaration.

What are the principles of Object-Oriented Programming (OOP) in Delphi?

The principles of OOP in Delphi are encapsulation, inheritance, and polymorphism. Encapsulation is the bundling of data and methods that manipulate the data. Inheritance is the ability of a class to inherit properties and methods from another class. Polymorphism is the ability of an object to take on many forms.

Describe the difference between public, private, and protected visibility in Delphi classes.

In Delphi classes, 'public' members can be accessed from anywhere, 'private' members can only be accessed from within the same class, and 'protected' members can be accessed from the same class and its descendants.

How would you use pointers in Delphi?

In Delphi, you can declare a pointer using the '^' symbol. You can then use the 'new' procedure to allocate memory for the pointer, and the 'dispose' procedure to free the memory when you're done.

What are the uses of Interfaces in Delphi?

Interfaces in Delphi are used to define a set of methods and properties that a class must implement. They provide a way to ensure that a class adheres to a certain contract, and they can also be used to achieve multiple inheritance.

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At this point, a skilled Delphi engineer should demonstrate strong problem-solving abilities, proficiency in Delphi 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 Delphi.

What does the following Delphi code do?
var
  s: string;
begin
  s := 'Hello, World!';
  ShowMessage(s);
end.
This code declares a string variable 's', assigns the value 'Hello, World!' to it, and then displays a message box with the value of 's'.
What will be the output of the following Delphi code?
var
  x, y, z: integer;
begin
  x := 5;
  y := 10;
  z := x + y;
  WriteLn(z);
end.
This code declares three integer variables 'x', 'y', and 'z'. It assigns the values 5 and 10 to 'x' and 'y' respectively. Then it adds 'x' and 'y' and assigns the result to 'z'. Finally, it prints the value of 'z'. The output will be 15.
What does the following Delphi code do?
var
  numbers: array[1..5] of integer;
begin
  numbers[1] := 1;
  numbers[2] := 2;
  numbers[3] := 3;
  numbers[4] := 4;
  numbers[5] := 5;
end.
This code declares an array 'numbers' of size 5. It then assigns the values 1 to 5 to the respective indices of the array.
What does the following Delphi code do?
var
  thread: TThread;
begin
  thread := TThread.CreateAnonymousThread(
    procedure
    begin
      WriteLn('Hello, World!');
    end
  );
  thread.Start;
end.
This code creates an anonymous thread that prints 'Hello, World!' to the console when started.

Wrap-up questions

Final candidate for Delphi 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 Delphi application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

Describe the difference between overloading and overriding in Delphi.

In Delphi, overloading is when you have multiple procedures or functions with the same name but different parameters. Overriding is when a descendant class provides a new implementation for a method inherited from an ancestor class.

How would you use generics in Delphi?

In Delphi, you can use generics to create classes, methods, or procedures that can work with different data types. You declare a generic using the '<>' syntax, and then use the generic type as a placeholder for the actual type.

What are the uses of attributes in Delphi?

Attributes in Delphi are used to add metadata to classes, methods, properties, and other elements. They can be used for a variety of purposes, such as controlling how elements are serialized, specifying design-time behavior, or providing hints for code analysis tools.

Delphi application related

Product Perfect's Delphi development capabilities

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

Delphi Consultive assessments

Delphi Application Conversion Assessment Delphi Application Integration Assessment Delphi Data & Database Integration Assessment

Custom Delphi development projects

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

Hiring guide for Delphi Engineers

Delphi Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

Delphi Consultive assessments

Custom Delphi development projects