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.
问题:
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:
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));
}