Multiple variable assignment in Swift

by

You don’t.

This is a language feature to prevent the standard unwanted side-effect of assignment returning a value, as described in the Swift book:

Unlike the assignment operator in C and Objective-C, the assignment operator in Swift does not itself return a value. The following statement is not valid:

   if x = y {
       // this is not valid, because x = y does not return a value
   }

This feature prevents the assignment operator (=) from being used by accident when the equal to operator (==) is actually intended. By making if x = y invalid, Swift helps you to avoid these kinds of errors in your code.

So, this helps prevent this extremely common error. While this kind of mistake can be mitigated for in other languages—for example, by using Yoda conditions—the Swift designers apparently decided that it was better to make certain at the language level that you couldn’t shoot yourself in the foot. But it does mean that you can’t use:

blah = blah2 = 3

If you’re desperate to do the assignment on one line, you could use tuple syntax, but you’d still have to specifically assign each value:

(blah, blah2) = (3, 3)

…and I wouldn’t recommend it. While it may feel inconvenient at first, just typing the whole thing out is the best way to go, in my opinion:

blah = 3
blah2 = 3

More Related Contents:

  1. Create a variable in swift with dynamic name
  2. How to get variable name?
  3. JavaScript OR (||) variable assignment explanation
  4. Why can’t I do assignment outside a method?
  5. Multiple left-hand assignment with JavaScript
  6. How do I do multiple assignment in MATLAB?
  7. Assign multiple new variables on LHS in a single line
  8. ViewController.Type does not have a member named
  9. Why are variables “i” and “j” used for counters?
  10. Which variable size to use (db, dw, dd) with x86 assembly?
  11. When should I quote CMake variables?
  12. Dynamically create variables in PowerShell
  13. If two variables point to the same object, why doesn’t reassigning one variable affect the other?
  14. In Rust, what’s the difference between “shadowing” and “mutability”?
  15. Static vs class functions/variables in Swift classes?
  16. LessCss dynamic variables based on ancestor class
  17. Powershell pass variable to start-job
  18. How to make points one color when a third column equals zero, and another color otherwise, in Gnuplot?
  19. Batch File Set Variable not working [duplicate]
  20. Why there are two ways of declaring variables in Go, what’s the difference and which to use?
  21. In MATLAB, are variables REALLY double-precision by default?
  22. Why are variables “i” and “j” used for counters?
  23. Dynamic Variable Naming and Reference (ColdFusion)
  24. Is a variable the name, the value, or the memory location?
  25. gnuplot store one number from data file into variable
  26. Is there anything like deal() for normal MATLAB arrays? [duplicate]
  27. Why does foo = filter(…) return a , not a list? [duplicate]
  28. Set fact with dynamic key name in ansible
  29. When should I quote CMake variable references?
  30. Test if an argument of a function is set or not in R

Leave a Comment