Change method of duplicate string in NSString.CacheContainer
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Previous commit did not pass some tests.
| @@ -54,8 +54,7 @@ extension NSString { | |||
| // | |||
| // A reference to `NSString` is held by every cast `String` along with their views and | |||
| // indices. | |||
| let cString = string.cStringUsingEncoding(NSUTF8StringEncoding) | |||
| let string = String(CString: cString, encoding: NSUTF8StringEncoding)! | |||
| let string = string.mutableCopy() as! String | |||
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Why is this mutableCopy() and not just copy()?
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NSString.copy returns self because that is immutable. NSString.mutableCopy returns new instance of NSString with copied buffer. On this case, the string holds reference of the CacheContainer through associated object.
On baa8a3a, ByteOffsetCache(renamed to CacheContainer) held reference of string by holding String.UTF8Index and that caused circular reference.
On 6656224, it resolved by changing to create new instance.
Using mutableCopy() replaces that.
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NSString(string: string) as String ?
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Thanks for the detailed explanation!
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@segiddins
Apple's document said:
- initWithString:
Returns an NSString object initialized by copying the characters from another given string.
But, you can confirm that is incorrect as following:
import Foundation
let str1 = "Hello, playground" as NSString
let str2 = NSString(string: str1)
let str3 = str1.mutableCopy() as! NSString
let id1 = ObjectIdentifier(str1)
let id2 = ObjectIdentifier(str2)
let id3 = ObjectIdentifier(str3)
id1 == id2 // true
id1 == id3 // false
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Thanks for the fix! I'm just not sure why it has to be a mutable copy. |
Change method of duplicate string in `NSString.CacheContainer`
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🙏 |
Fix realm/SwiftLint#379