Add post about two types of Swift macros

content/posts/two-types-of-swift-macros/index.md

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+---
+title: 'Two types of Swift macros'
+date: 2024-11-26
+tags: ['Swift', 'Macro']
+cover: 
+  image: 'images/cover.png'
+  alt: 'Two types of Swift macros'
+---
+
+Explain `#` and `@` in Swift - your next interview may have this question! Don't miss it out!
+
+Shortly - `#` and `@` are prefixes for macros in Swift.
+
+What is macro?
+💡 Macro is a feature that generates code during compilation. Unlike macros in C, which work like “find and replace”, Swift macros are type-safe and context aware, making them powerful tools reducing boilerplate code.
+
+Two types of macros
+1️⃣ attached - use `@` prefix, tied to a declaration adding extra logic to it, like: `@Test`, `@Model`, `@Observable`
+2️⃣ freestanding - use `#` prefix, standalone code like `#expect`, `#Predicate`, `#warning`
+
+Example of attached macro ⤵️
+```swift
+@Test func addition() { // tied to the declaration
+    ...
+}
+```
+
+Example of freestanding macro ⤵️
+```swift
+@Test func addition() {
+    #require(1 + 2 == 3) // not attached to a declaration
+}
+```
+
+Bonus:
+It’s possible to expand macros (especially the ones defined by you) and check what’s the implementation inside. ⤵️
+
+![Expanded_macro](images/expand_macro.gif)
+
+---
+
+Thanks for reading. 📖
+
+I hope you found it useful!
+
+If you enjoy the topic don't forget to follow me on one of my social media - [LinkedIn](https://www.linkedin.com/in/maciej-gomolka/), [X](https://twitter.com/gomolka_maciej) or via [RSS](https://www.mobiledevdiary.com/index.xml) feed to keep up to speed. 🚀