String value to UnsafePointer function parameter behavior

by

This is working because of one of the interoperability changes the Swift team has made since the initial launch – you’re right that it looks like it hasn’t made it into the documentation yet. String works where an UnsafePointer<UInt8> is required so that you can call C functions that expect a const char * parameter without a lot of extra work.

Look at the C function strlen, defined in “shims.h”:

size_t strlen(const char *s);

In Swift it comes through as this:

func strlen(s: UnsafePointer<Int8>) -> UInt

Which can be called with a String with no additional work:

let str = "Hi."
strlen(str)
// 3

Look at the revisions on this answer to see how C-string interop has changed over time: https://stackoverflow.com/a/24438698/59541

More Related Contents:

  1. Set operations in swift
  2. How to lock orientation of one view controller to portrait mode only in Swift
  3. Examples of Delegates in Swift [closed]
  4. How to create USDZ file using Xcode converter?
  5. NSDate Comparison using Swift
  6. How to test equality of Swift enums with associated values
  7. dyld: Library not loaded: @rpath/libswift_stdlib_core.dylib
  8. Using Decodable in Swift 4 with Inheritance
  9. Is it possible to add type constraints to a Swift protocol conformance extension?
  10. Accessing an Enumeration association value in Swift
  11. Strange Swift numbers type casting
  12. Dictionary wrong order – JSON
  13. How to hash NSString with SHA1 in Swift?
  14. How to apply the type to a NSFetchRequest instance?
  15. SwiftUI iterating through dictionary with ForEach
  16. Choosing CoreData Entities from form picker
  17. Iterate over collection two at a time in Swift
  18. unwrapping multiple optionals in if statement
  19. USB Connection Delegate on Swift
  20. How do you use .enumerated() with ForEach in SwiftUI?
  21. Value of type ‘StorageMetadata’ has no member ‘downloadURL’
  22. How to pass one SwiftUI View as a variable to another View struct
  23. iOS13 Navigation bar large titles not covering status bar
  24. How to access NSWindow from @main App using only SwiftUI?
  25. Use Cocoapods with an App Extension
  26. How to remove “row” separators/dividers from a List in SwiftUI?
  27. Increase the size of the indicator in UIPageViewController’s UIPageControl
  28. How do I programmatically move an ARAnchor?
  29. Self in init params
  30. Whats the Swift animate WithDuration syntax?

Leave a Comment