Decoding Dictionaries: From Basics to Interview-Ready

Name: Decoding Dictionaries: From Basics to Interview-Ready
Rating: 5.0 (1 reviews)

Learn Swift dictionaries from the ground up—perfect for beginners, job prep, and real iOS project work.

Created byNorbert Grover

Last updated 8/2025

English

What you'll learn

Understand how to create and access Swift dictionaries effectively.
Safely unwrap and work with optional dictionary values.
Use default values to avoid crashes when accessing keys.
Group data using dictionaries for real-world scenarios.
Merge, map, and filter dictionaries in Swift.
Solve common interview problems using dictionaries.
Decode JSON into dictionaries using Swift’s Codable system.
Build dynamic lookup tables using key-value storage.
Reverse dictionary mappings with confidence.
Apply dictionary logic to SwiftUI and state management.

Course content

1 section • 31 lectures • 2h 58m total length

Introduction2:32
This is an introduction to the dictionaries course.
Why dictionaries matter.1:19
By the end of this course, you will:
Understand how dictionaries work and when to use them
Apply dictionary techniques to solve interview-style problems
Build confidence in using Swift dictionaries for real-world tasks
Grouping Values by a Property8:16
In this tutorial, you'll learn how to group custom objects by an attribute using Swift dictionaries. We'll walk through a real-world example using a custom Fighter struct and show how to organize fighters by the organizations they belong to. This lesson is ideal for those looking to deepen their understanding of dictionaries, loops, and data transformation in Swift—especially for interview preparation or iOS development practice.
Topics covered:
Custom struct definitions
Nested loops and data extraction
Dictionary initialization and value appending
Practical grouping logic for real-world data
By the end of the video, you'll be able to confidently group custom Swift objects by any of their attributes. Perfect for junior and intermediate Swift developers.
Coding Challenge: Student Gradebook8:30
Scenario:
You're building a simple grade tracking system for a classroom app. Each student can have multiple test scores. Your task is to compute the average score for each student using a dictionary.
Coding Challenge: Inventory Tracker3:01
Scenario:
You're developing an app for a small retail business to track product inventory. Each product has a name and a quantity in stock. Sometimes, multiple shipments arrive with the same product name, and you need to aggregate the quantities.
Advanced Coding Challenge: Inventory by Warehouse4:42
Scenario:
You're now tracking inventory not just by product name, but also by the warehouse location where each shipment is received. You need to organize the data so that you can view the inventory per product for each warehouse.
Coding Challenge: Most Active Users3:20
Write a function called countUserActivity that takes an array of UserAction and returns a dictionary of type [String: Int].
Each key should be a username, and the value should be the total number of actions they performed.
Coding Challenge: Top Performer by Subject0:35
Scenario:
You're managing student performance data across multiple subjects. Each score entry contains a student's name, the subject, and their score on a test. Your goal is to identify the top-scoring student in each subject.
Solution: Top Performers by Subject19:28
Scenario:
You're managing student performance data across multiple subjects. Each score entry contains a student's name, the subject, and their score on a test. Your goal is to identify the top-scoring student in each subject.
Coding Challenge: Normalize Event Logs0:35
You're analyzing system logs from a distributed application. Each log entry includes the name of the server where the event occurred and a list of error codes encountered. Your task is to create a dictionary that maps each error code to the list of servers where it occurred, without duplicates.
Solution: Normalize Event Logs11:22
You're analyzing system logs from a distributed application. Each log entry includes the name of the server where the event occurred and a list of error codes encountered. Your task is to create a dictionary that maps each error code to the list of servers where it occurred, without duplicates. This is the coding demonstration.
Coding Challenge: Team Points Leaderboard0:38
Scenario:
You're managing match results for a local sports league. Each game has a home team, away team, and the final scores. Your goal is to generate a leaderboard showing total points per team, where:
A win gives 3 points
A draw gives 1 point
A loss gives 0 points
Solution: Team Points Leaderboard10:49
Scenario:
You're managing match results for a local sports league. Each game has a home team, away team, and the final scores. Your goal is to generate a leaderboard showing total points per team, where:
A win gives 3 points
A draw gives 1 point
A loss gives 0 points
I will be coding the solution to this problem.
Coding Challenge: Highest Sale by Salesperson0:29
You’re working with sales data from a team of salespeople. Each sale record includes the salesperson's name and the sale amount. Your goal is to find the highest single sale made by each person.
Solution: Highest Sale by Salesperson6:33
You’re working with sales data from a team of salespeople. Each sale record includes the salesperson's name and the sale amount. Your goal is to find the highest single sale made by each person. The coding of the solution provides and explanation of the code.
Coding Challenge: Most Common Reaction Per Post0:33
You're analyzing user reactions on a social media platform. Each reaction is tied to a specific post and includes the type of reaction (like "like", "love", "angry", etc.). Your task is to determine the most common reaction for each post.
Solution: Most Common Reaction Per Post17:05
You're analyzing user reactions on a social media platform. Each reaction is tied to a specific post and includes the type of reaction (like "like", "love", "angry", etc.). Your task is to determine the most common reaction for each post. Now let's demonstrate coding the solution.
Coding Challenge: First Responder Tracker0:37
You're analyzing emergency response data. Each response record includes the name of the responder, the city where they responded, and how many minutes they took to arrive. Your task is to determine the fastest responder for each city — that is, the person who responded in the shortest time.
Solution: First Responder Tracker13:17
You're analyzing emergency response data. Each response record includes the name of the responder, the city where they responded, and how many minutes they took to arrive. Your task is to determine the fastest responder for each city — that is, the person who responded in the shortest time. Demonstrating coding the solution.
Coding Challenge: Course Completion Tracker0:41
You're analyzing student progress data for an online course platform. Each student log records a student’s name, the course name, and whether they completed it. Your goal is to build a report showing, for each course, which students have completed it.
Solution: Course Completion Tracker7:26
You're analyzing student progress data for an online course platform. Each student log records a student’s name, the course name, and whether they completed it. Your goal is to build a report showing, for each course, which students have completed it.
Coding Challenge: Average Rating by Product0:33
You’re building an analytics feature for an e-commerce app. Each user review includes the product name and a rating from 1 to 5. Your task is to calculate the average rating for each product and return the results as a dictionary.
Solution: Average Rating by Product8:55
You’re building an analytics feature for an e-commerce app. Each user review includes the product name and a rating from 1 to 5. Your task is to calculate the average rating for each product and return the results as a dictionary.
Coding Challenge: Employee Project Tracker0:34
You're analyzing user session data from a mobile app. Each session record includes the username and the number of minutes they were active. Your task is to find the total active time per user but only include users who had at least one session over 10 minutes (to filter out quick logins or pings).
Solution: Employee Project Tracker7:03
You're analyzing user session data from a mobile app. Each session record includes the username and the number of minutes they were active. Your task is to find the total active time per user but only include users who had at least one session over 10 minutes (to filter out quick logins or pings).
Coding Challenge: Word Frequency by Author0:39
You're building a feature for a blogging platform to analyze vocabulary usage. Each blog post includes the author's name and the post content. Your task is to count how often each word appears per author (ignoring punctuation and case sensitivity).
Solution: Word Frequency by Author14:25
You're building a feature for a blogging platform to analyze vocabulary usage. Each blog post includes the author's name and the post content. Your task is to count how often each word appears per author (ignoring punctuation and case sensitivity).
Coding Challenge: Longest Message by User0:33
You're analyzing messages from a chat system. Each message record includes the username and the message content. Your task is to determine the longest message sent by each user.
Solution: Longest Message by User15:43
You're analyzing messages from a chat system. Each message record includes the username and the message content. Your task is to determine the longest message sent by each user.
Coding Challenge: Daily Expense Tracker0:39
You’re working with personal finance data. Each expense record includes the user's name, a date string, and the amount spent. Your goal is to compute the total amount spent per user per day.
Solution: Daily Expense Tracker7:34
You’re working with personal finance data. Each expense record includes the user's name, a date string, and the amount spent. Your goal is to compute the total amount spent per user per day.

Requirements

Basic understanding of Swift syntax (variables, conditionals, loops).
Familiarity with arrays and simple data structures in Swift.
Experience writing functions and working with optionals.
Ability to run Swift code in Xcode or a Swift Playground.
Some exposure to how JSON data is structured (helpful but not required).
Comfort reading documentation and exploring examples independently.
A Mac with Xcode installed (version 13 or higher recommended).
No need for UIKit or SwiftUI experience—this course is logic-focused.
Ideal for beginners with a few weeks of Swift behind them.
No prior experience with dictionaries required—this course starts at the foundation.

Description

Dictionaries are one of the most essential tools in Swift, yet most iOS development courses barely scratch the surface. They show up in passing, but few—if any—courses are dedicated to mastering them. This course is different.

Decoding Dictionaries: From Basics to Interview-Ready is the only course on the market that puts Swift dictionaries front and center, showing you how to manipulate, transform, and solve real problems with them. In the world of iOS development, being able to group, filter, restructure, and decode dictionary-based data is not just helpful—it’s critical.

Most online courses are built around what sells. This course is built around what you actually need to know to succeed as a mobile developer. If you’re serious about building clean, efficient, and interview-ready Swift code, this course gives you the skills that hiring managers quietly expect but few bootcamps or tutorials ever teach.

What You’ll Learn:

Creating and safely accessing key-value data
Grouping, merging, mapping, and filtering dictionary content
Building dictionary-powered algorithms for real-world use
Solving common interview-style coding challenges using dictionaries
Parsing and decoding JSON into dictionaries using Codable
Using dictionaries to manage view state, model data, and more

Coding Challenges Include:

Grouping articles by tags
Counting word frequency from text input
Reversing a dictionary’s key-value pairs
Filtering based on nested keys and optional values
Building lookup tables dynamically
Custom decoding of nested JSON dictionaries

By the end of this course, you’ll have the fluency and confidence to use dictionaries not just to pass coding challenges—but to build production-ready features and think like a professional Swift developer.

Who this course is for:

Swift beginners who struggle with understanding dictionaries.
iOS developers preparing for technical interviews involving data manipulation.
Self-taught developers who feel their foundation in Swift is incomplete.
Students looking to improve their problem-solving skills with real coding challenges.
Developers transitioning from another language who need to master Swift dictionaries.
Junior iOS engineers who want to write cleaner, more efficient Swift code.
Programmers overwhelmed by JSON decoding and key-value data handling.
Learners who are confident with arrays but unsure how to leverage dictionaries.
Developers seeking practical, hands-on Swift practice outside of UI-heavy courses.
Anyone tired of surface-level tutorials and ready to go deeper with Swift fundamentals.