- 01Getting Started
- 02Your First Output (print)
- 03Working with Variables
- 04Conditionals (if statements)
- 05Loops (for-in statements)
- 06Writing a Function
- 07Working with Arrays
- 08Loops (while statements)
- 09Classes (Object-Oriented Programming)
- 10Error Handling (do-try-catch)
- 11Sorting an Array
- 12Recursive Functions
- 13Using the Standard Library
- 14The switch Statement
- 15The Ternary Operator
- 16Inheritance (Extending a Class)
- 17Writing Comments
- 18Logical Operators (&&, ||, !)
- 19Constants (let, and why it matters)
- 20Splitting and Joining Strings (split, joined)
- 21Optionals (Writing nil-Safe Code)
- 22Searching an Array (contains, first)
- 23Transforming an Array (map)
- 24Two-Dimensional Arrays (Tabular Data)
- 25Writing a Custom Error Type
- 26Default Parameter Values
- 27Working with Set
- 28Checking Correctness (Your First Step into Testing)
- 29Higher-Order Functions (Passing a Function as an Argument)
- 30Stacks and Queues (Basic Data Structures)
- 31Type Conversion (Casting) Basics
- 32Intro to Regular Expressions (Pattern Matching)
- 33The Binary Search Algorithm
- 34Building a Caesar Cipher (a Character-Shifting Cipher)
- 35Understanding How Bubble Sort Works
- 36Building and Displaying Dates (Basic Year/Month/Day Operations)
- 37Writing Multiple Test Cases Together
- 38Speeding Up Calculations with Memoization (Caching)
- 39Normalizing Strings (trimmingCharacters, Unifying Case)
- 40Shallow Copy vs. Deep Copy
- 41Enum (Enumerated Types) Basics
- 42Flattening an Array
- 43Reversing a String and Checking for Palindromes
- 44Pairing Up Two Arrays (the zip operation)
- 45Rounding Numbers (rounded)
- 46Multi-Line Strings (Triple Quotes)
- 47Functions That Return Multiple Values (Tuples)
- 48Finding the GCD and LCM (the Euclidean Algorithm)
- 49Formatting Numbers (Padding Digits, Decimal Places)
- 50Cleanup Logic with defer
- 51Writing Generic Functions
- 52File Reading and Writing Basics
- 53Generating Random Numbers
- 54Bitwise Operators (AND, OR, XOR, shifts)
- 55Reading Command-Line Arguments
- 56Waiting for a Fixed Amount of Time (Thread.sleep)
- 57Watch Out for Floating-Point Rounding Errors
- 58Reading from Standard Input
- 59FizzBuzz (the Classic Practice Problem)
- 60Checking Whether a Number Is Prime
- 61Set Operations with Set (Union, Intersection, Difference)
- 62Converting Number Bases (Binary, Hex)
- 63Checking Balanced Parentheses (an Application of Stacks)
- 64Checking Whether Two Words Are Anagrams
- 65Checking Whether a Year Is a Leap Year
- 66Converting Temperature (Celsius to Fahrenheit)
- 67Prime Factorization
- 68[Applied] Build a Simple Inventory Management Tool
Formatting Numbers (Padding Digits, Decimal Places)
In this lesson you will learn how to format numbers in Swift with String(format:), lining up digits and decimal places so values display neatly. This is for anyone searching for "Swift String format how to use".
String(format: "%.2f", value) fixes the number of decimal places and String(format: "%03d", value) pads the front of a number with zeros. Both are handy for displaying amounts or generating numbered file names.
The sample code turns 1234.5 into "1234.50 dollars" with two decimal places via String(format: "%.2f dollars", price), and turns 7 into the zero-padded "007" via String(format: "%03d", num).
A common stumbling block for beginners is the sheer number of format specifiers. There are %f for floating-point numbers, %d for integers, and many more, and you have to pick the one that fits.
In real-world development, raw calculation results have wildly varying widths, so applying this kind of formatting right before display is standard practice.
๐งช This site can't compile or run Swift directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser โ nothing is sent anywhere).