Converting a CGPoint to NSValue

问题

In CABasicAnimation.fromValue I want to convert a CGPoint to a "class" so I used NSValue valueWithPoint but in device mode or simulator one is not working... need to use NSMakePoint or CGPointMake if in device or simulator.

回答1:

There is a UIKit addition to NSValue that defines a function

+ (NSValue *)valueWithCGPoint:(CGPoint)point

See iPhone doc

回答2:

@ashcatch 's answer is very helpful, but consider that those methods from addition copy values, when native NSValue methods store pointers! Here is my code checking it:

CGPoint point = CGPointMake(2, 4);
NSValue *val = [NSValue valueWithCGPoint:point];
point.x = 10;
CGPoint newPoint = [val CGPointValue];

here newPoint.x = 2; point.x = 10

CGPoint point = CGPointMake(2, 4);
NSValue *val = [NSValue valueWithPointer:&point];
point.x = 10;
CGPoint *newPoint = [val pointerValue];

here newPoint.x = 10; point.x = 10

回答3:

In Swift, you can change a value like this:

    var pointValueare = CGPointMake(30,30)
    NSValue(CGPoint: pointValueare)

回答4:

&(cgpoint) -> get a reference (address) to cgpoint (NSPoint *)&(cgpoint) -> casts that reference to an NSPoint pointer *(NSPoint )(cgpoint) -> dereferences that NSPoint pointer to return an NSPoint to make the return type happy

回答5:

In Swift the static method is change to an initialiser method:

var pointValue = CGPointMake(10,10)
NSValue(CGPoint: pointValue)

回答6:

If you are using a recent-ish version of Xcode (post 2015), you can adopt the modern Objective-C syntax for this. You just need to wrap your CGPoint in @():

CGPoint primitivePoint = CGPointMake(4, 6);
NSValue *wrappedPoint = @(primitivePoint);

Under the hood the compiler will call +[NSValue valueWithCGPoint:] for you.

https://developer.apple.com/library/archive/releasenotes/ObjectiveC/ModernizationObjC/AdoptingModernObjective-C/AdoptingModernObjective-C.html

回答7:

Don't think of it as "converting" your point-- NSValue is a wrapper class that holds primitive structs like NSPoint. Anyway, here's the function you need. It's part of Cocoa, but not Cocoa Touch. You can add the entire function to your project, or just do the same conversion wherever you need it.

NSPoint NSPointFromCGPoint(CGPoint cgpoint) {
   return (*(NSPoint *)&(cgpoint));
}

来源：https://stackoverflow.com/questions/772958/converting-a-cgpoint-to-nsvalue

标签

objective-c

iphone

cgpoint

nsvalue