Learn Swift from scratch Learning Notes (day)--core Foundation framework memory managed Objects vs. unmanaged objects

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Memory managed Objects

Swift called in corefoundation when a function obtains an object, the object is divided into: a memory managed object and a memory unmanaged object.

cfretain cfrelease

The way to get these memory managed objects is to use the cf_returns_retained or cf_returns_not_retained note Declaration, sample code:

-(CGPathRef)makeToPath CF_RETURNS_RETAINED

{

    UIBezierPath* triangle = [UIBezierPath bezierPath];

    [triangle moveToPoint:CGPointZero];

    [triangle addLineToPoint:CGPointMake(self.view.frame.size.width,0)];

    [triangle addLineToPoint:CGPointMake(0, self.view.frame.size.height)];

    [triangle closePath];

    CGPathRef theCGPath = [triangle CGPath];

    return CGPathCreateCopy(theCGPath);

}

Memory managed objects are simple to use and do not require us to do extra things.

func CFStringCreateWithCString (_ alloc: CFAllocator !,

         _ cStr: UnsafePointer <Int8>,

          _ encoding: CFStringEncoding)-> CFString! // Memory managed object

 

func CFHostCreateCopy (_ alloc: CFAllocator ?,

          _ host: CFHost)-> Unmanaged <CFHost> // Memory unmanaged object

Memory unmanaged objects

memory unmanaged objects are memory that needs to be managed by the programmer himself. This is because the method in which the object was obtained is not usedcf_returns_retainedorcf_returns_not_retainedComment Declaration, the compiler cannot help manage memory. We can use the previous section to determine whether a non-memory managed object is used in a specific way .

Memory Unmanaged objects are a bit cumbersome to use and should be handled according to the method of acquiring ownership.

1.If a function name containsCreateorCopy, the caller obtains the object 's ownership at the same time, and the return value unmanaged<t>need to callTakeretainedvalue ()method to obtain the object. When the caller no longer uses the object,Swiftthe code needs to callCfreleasefunction discards the ownership of the object becauseSwiftis aARCmemory-managed.

2.If a function name containsGet, the caller obtains the object without taking ownership of the object, and the return value unmanaged<t>need to callTakeunretainedvalue ()method to obtain the object.

The sample code is as follows:

let host: CFHost = CFHostCreateWithName(kCFAllocatorDefault, 

        ê"127.0.0.1").takeRetainedValue()

        

let hostNames: CFArray = CFHostGetNames(host, nil)!.takeUnretainedValue()

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Learn Swift from scratch Learning Notes (day)--core Foundation framework memory managed Objects vs. unmanaged objects