Concepts in Mobile Dev
React Native Core Components: Your UI Building Blocks
Think of Core Components as React Native's built-in LEGO bricks for UIs, translating your code into native Android and iOS views. Use them for layouts (View), text (Text), and lists (FlatList). The footgun: never use ScrollView for long lists.
Variables and Constants in Swift
Swift has two ways to store a value: var declares a variable you can reassign later, and let declares a constant whose value is set once and can never change, and Swift's convention is to default to let unless you have a specific reason to need var.
Dart Variables: var, final, and const
In Dart, var creates a mutable variable, while final and const are for single-assignment. Use var for changing state, final for runtime values set once, and const for compile-time constants. The footgun is confusing final with const.
Kotlin Variables: `val` for Constants, `var` for Variables
In Kotlin, val creates a read-only constant you assign once, like a fixed setting. var creates a mutable variable you can change later. Always prefer val unless you explicitly need to reassign a value to prevent accidental state changes.
Styling in React Native with StyleSheet
StyleSheet is React Native's answer to CSS, defining styles in JavaScript to separate presentation from logic. Use StyleSheet.create() to define reusable style objects that get static type checking. The footgun is styling inline, which hurts performance.
Swift Control Flow: Directing Your Code's Path
Control flow statements are the traffic signals of your code. They use keywords like if, for, and switch to make decisions and repeat actions, rather than just running top-to-bottom. This is how you show a list of items or check if a user is logged.
Dart's Core Data Types: Everything is an Object
In Dart, everything is an object, from numbers to functions. This means even a simple int or String has methods and properties, unlike primitive types in other languages. The main footgun is forgetting that null itself is a type, Null.
Kotlin Null Safety: Catch Nulls at Compile Time
Kotlin's type system catches null pointer errors at compile time. Variables are non-nullable by default; you must opt-in to nulls with a ? (e.g., String?). The compiler then forces you to handle the null case. The main footgun is the !! operator.
Kotlin's Control Flow Expressions: `if` and `when`
In Kotlin, if and when are expressions that return a value. This lets you assign their result directly to a variable, replacing Java's ternary operator. The footgun: when used as an expression, you must have an else branch to cover all cases.
Flexbox: Responsive Layouts in React Native
Flexbox arranges components along a primary axis, creating responsive UIs without manual calculations. It's used for nearly all layout needs, from centering items to building complex grids.
Swift Optionals: Handling Nothing Safely
An Optional is like a box that might contain a value or might be empty (nil). You must safely unwrap it before using the value, preventing crashes. It's used for properties that might not exist yet or for function returns that can fail.
Dart's Control Flow: Telling Your Code What to Do Next
Control flow statements are the road signs for your code, directing execution beyond a simple top-to-bottom path. Use if/else for decisions, for/while for loops, and try/catch to handle errors. The footgun is forgetting break in a switch case.
Metro: The JavaScript Bundler for React Native
Metro bundles your React Native app's JavaScript, finding all modules, transpiling them for the device, and merging them into one file. It's what powers npx react-native start.
Swift Structs vs. Classes: Value vs. Reference Types
In Swift, a struct is a copied value (like a new document), while a class is a shared reference (like a link to one document). Use structs for simple data like coordinates; use classes for shared state like a user session.
Dart Function Syntax: Block Body vs. Arrow Notation
Dart functions use a block body {} for multiple statements or arrow syntax => for a single expression. Use => for simple one-liners like bool isEven(int n) => n % 2 == 0;. The footgun is using => for multi-step logic; it only works for.
Kotlin Functions: Named, Reusable Code Blocks
A function is a named recipe for your code. You give it ingredients (parameters) and it produces a result. They are used everywhere, from calculating values to handling button clicks.
Swift Enums: Type-Safe Choice Modeling
A Swift enum is a closed menu of possibilities the compiler tracks exhaustively. Use it to replace string constants or model a network result state. Adding a case without updating every switch breaks compile-time safety if you rely on a default clause.
React Native: Platform-Specific Code
React Native lets you write platform-specific logic without ejecting. Use the Platform module for small style tweaks, and file extensions (.ios.js) for swapping entire components. The footgun is overusing Platform.select for complex UI, creating clutter.
Dart Collections: Choosing List, Set, or Map
Dart collections organize data: use a List for ordered items, a Set for unique items, and a Map for key-value pairs. This choice is fundamental for storing UI widgets or parsing JSON. The common footgun is using a List for lookups, which is slow; use.
Kotlin Inheritance: Open for Extension, Closed by Default
In Kotlin, classes are final by default. Think of inheritance as an opt-in feature you enable with the open keyword. Use it to create specialized versions of a base class, like a Student from a Person.
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