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| author | Divay Prakash <divayprakash@users.noreply.github.com> | 2020-01-24 20:12:10 +0530 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-01-24 20:12:10 +0530 |
| commit | 87669f1c7c40f6ab3ad70bf723cc396979f96306 (patch) | |
| tree | 05dea704c60d14e3cc7f68a61116b1c3d6456ec4 | |
| parent | 73338166dfab5e44c67ee6f456811098ed109fb3 (diff) | |
| parent | 9c18774c349cbb0821f59f77c6fff3908139bff7 (diff) | |
Merge pull request #3755 from hamidra/patch-3
[swift/en-us] add downcast to the tutorial
| -rw-r--r-- | swift.html.markdown | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/swift.html.markdown b/swift.html.markdown index 1f9fe897..8582131a 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -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") |