info/learnxinyminutes-docs
1
0
Fork 0
mirror of https://github.com/adambard/learnxinyminutes-docs.git synced 2025-08-11 09:14:39 +02:00
Code Issues Releases Wiki Activity

Merge pull request #3755 from hamidra/patch-3

Browse Source 
[swift/en-us] add downcast to the tutorial
This commit is contained in:
Divay Prakash
2020-01-24 20:12:10 +05:30
committed by GitHub
parent 73338166df 9c18774c34
commit 87669f1c7c
1 changed files with 5 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
swift.html.markdown
View File

@@ -692,6 +692,11 @@ print(mySquare.sideLength) // 4
// cast instance
let aShape = mySquare as Shape
// downcast instance:
// Because downcasting can fail, the result can be an optional (as?) or an implicitly unwrpped optional (as!).
let anOptionalSquare = aShape as? Square // This will return nil if aShape is not a Square
let aSquare = aShape as! Square // This will throw a runtime error if aShape is not a Square
// compare instances, not the same as == which compares objects (equal to)
if mySquare === mySquare {
print("Yep, it's mySquare")