Instance Method

Adds an arc of a circle to the path, specified with a radius and angles.

## Parameters

`center`

The center of the arc, in user space coordinates.

`radius`

The radius of the arc, in user space coordinates.

`startAngle`

The angle to the starting point of the arc, measured in radians from the positive x-axis.

`endAngle`

The angle to the end point of the arc, measured in radians from the positive x-axis.

`clockwise`

`true` to make a clockwise arc; `false` to make a counterclockwise arc.

`transform`

An affine transform to apply to the arc before adding to the path. Defaults to the identity transform if not specified.

## Discussion

This method calculates starting and ending points using the radius and angles you specify, uses a sequence of cubic Bézier curves to approximate a segment of a circle between those points, and then appends those curves to the path.

The `clockwise` parameter determines the direction in which the arc is created; the actual direction of the final path is dependent on the `transform` parameter and the current transform of a context where the path is drawn. In a flipped coordinate system (the default for UIView drawing methods in iOS), specifying a clockwise arc results in a counterclockwise arc after the transformation is applied.

If the path already contains a subpath, this method adds a line connecting the current point to the starting point of the arc. If the current path is empty, this method creates a new subpath whose starting point is the starting point of the arc. The ending point of the arc becomes the new current point of the path.

### Constructing a Graphics Path

`func move(to: CGPoint, transform: CGAffineTransform)`

Begins a new subpath at the specified point.

`func addLine(to: CGPoint, transform: CGAffineTransform)`

Appends a straight line segment from the current point to the specified point.

`func addLines(between: [CGPoint], transform: CGAffineTransform)`

Adds a sequence of connected straight-line segments to the path.

`func addRects([CGRect], transform: CGAffineTransform)`

Adds a set of rectangular subpaths to the path.

`func addEllipse(in: CGRect, transform: CGAffineTransform)`

Adds an ellipse that fits inside the specified rectangle.

`func addArc(tangent1End: CGPoint, tangent2End: CGPoint, radius: CGFloat, transform: CGAffineTransform)`

Adds an arc of a circle to the path, specified with a radius and two tangent lines.

`func addCurve(to: CGPoint, control1: CGPoint, control2: CGPoint, transform: CGAffineTransform)`

Adds a cubic Bézier curve to the path, with the specified end point and control points.

`func addQuadCurve(to: CGPoint, control: CGPoint, transform: CGAffineTransform)`

Adds a quadratic Bézier curve to the path, with the specified end point and control point.

`func closeSubpath()`

Closes and completes a subpath in a mutable graphics path.

Beta Software

This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.