升级到Swift 1.2 / Xcode 6.3后moveToPoint失败

Question

I've created a sub class of a UIView in which I draw a graph. I made it a public class so I can pass it new data and have it update when needed.

It all worked perfectly until I upgraded to Xcode 6.3 / Swift 1.2. Now when that view attempts to render my app crashes.

The error I get is:

Assertion failed: (CGFloatIsValid(x) && CGFloatIsValid(y)), function void CGPathMoveToPoint(CGMutablePathRef, const CGAffineTransform *, CGFloat, CGFloat), file Paths/CGPath.cc, line 254.

Here is my code for the class:

import UIKit

public class GraphView: UIView {

    //Data from parent VC
    var graphPoints = [0, 0, 0, 0, 0, 0, 0]
    var keyColor = BabyMasterStyleKit.bathsBase

    override public func drawRect(rect: CGRect) {

        let context = UIGraphicsGetCurrentContext()
        let colorSpace = CGColorSpaceCreateDeviceRGB()

        let width = rect.width
        let height = rect.height

        //calculate the x point

        let margin:CGFloat = 15.0
        var columnXPoint = { (column:Int) -> CGFloat in
            //Calculate gap between points
            let spacer = (width - margin*2 - 4) /
                CGFloat((self.graphPoints.count - 1))
            var x:CGFloat = CGFloat(column) * spacer
            x += margin + 2
            return x
        }

        // calculate the y point

        let topBorder:CGFloat = 15
        let bottomBorder:CGFloat = 15
        let graphHeight = height - topBorder - bottomBorder
        let maxValue = maxElement(graphPoints)
        var columnYPoint = { (graphPoint:Int) -> CGFloat in
            var y:CGFloat = CGFloat(graphPoint) /
                CGFloat(maxValue) * graphHeight
            y = graphHeight + topBorder - y // Flip the graph
            return y
        }

        //Draw horizontal graph lines on the top of everything
        var linePath = UIBezierPath()

        //top line
        linePath.moveToPoint(CGPoint(x:0, y: topBorder))
        linePath.addLineToPoint(CGPoint(x: width,
            y:topBorder))

        //center line
        linePath.moveToPoint(CGPoint(x:0,
            y: graphHeight/2 + topBorder))
        linePath.addLineToPoint(CGPoint(x:width,
            y:graphHeight/2 + topBorder))

        let color = UIColor.lightGrayColor()
        color.setStroke()

        linePath.lineWidth = 0.5
        linePath.stroke()

        // draw the line graph

        keyColor.setFill()
        keyColor.setStroke()

        // set up the points line
        var graphPath = UIBezierPath()
        // go to start of line
        graphPath.moveToPoint(CGPoint(x:columnXPoint(0), y:columnYPoint(graphPoints[0])))

        // add points for each item in the graph points array
        // at the correct (x, y) for the point
        for i in 1..<graphPoints.count {
            let nextPoint = CGPoint(x:columnXPoint(i),
                y:columnYPoint(graphPoints[i]))
            graphPath.addLineToPoint(nextPoint)
        }

        graphPath.stroke()

        //Draw the circles on top of graph stroke
        for i in 0..<graphPoints.count {
            var point = CGPoint(x:columnXPoint(i), y:columnYPoint(graphPoints[i]))
            point.x -= 5.0/2
            point.y -= 5.0/2

            let circle = UIBezierPath(ovalInRect:
                CGRect(origin: point,
                    size: CGSize(width: 6.0, height: 6.0)))
            circle.fill()
        }

        // add left and bottom borders
        UIColor.lightGrayColor().setStroke()

        var borderPath = UIBezierPath()
        borderPath.moveToPoint(CGPoint(x:0, y:0))
        borderPath.addLineToPoint(CGPoint(x:0, y:height))
        borderPath.addLineToPoint(CGPoint(x:width, y:height))
        borderPath.stroke()
    }

}

The app fails at this line:

graphPath.moveToPoint(CGPoint(x:columnXPoint(0), y:columnYPoint(graphPoints[0])))

The array graphPoints is the data I am passing in. I have it set to all 0s as a default. In my ViewController I have a function that passes in an array of real data (7 different numbers) and then does a setNeedsDislay() to re-render the view as needed.

Thanks for your help.

Answer 1

When the input array is

var graphPoints = [0, 0, 0, 0, 0, 0, 0]

then

let maxValue = maxElement(graphPoints)

makes maxValue 0, so that the line in columnYpoint

var y:CGFloat = CGFloat(graphPoint) / CGFloat(maxValue) * graphHeight

does a divide-by-zero and makes y a NaN . It's a special case of having all zero elements in the initial array.

Answer 2

I think the default graphPoints array was being ignored, so when the view first loaded it didn't have values (though it did show that it was passing a 0 into the columnYPoint function, so who knows). As a work around I just tested for y.isNAN and if it was set it to equal 0. After I did that everything worked.

edit: Just checked to see if in fact the default array for graphPoints was getting ignored, and it wasn't. I think that it just doesn't like that it was being passed in a 0 value. If anyone has an idea as to why this would be, I'd love to hear about it.