ObjectiveC mutableCopy如何快速运行

Question

我是Swift和iOS开发中的新成员。最近我试图用Swift编写一个使用CorePlot（用ObjectiveC编写）的iOS应用程序。我试图在Swift中重写一个CorePlot iOS示例代码（在http://www.raywenderlich.com/13271/how-to-draw-graphs-with-core-plot-part-2中找到）。有这样一行样品的ObjectiveC：

CPTMutableLineStyle *aaplLineStyle = [aaplPlot.dataLineStyle mutableCopy]; 
aaplLineStyle.lineWidth = 2.5; 

，我试图重写这样的：

var lineStyle = aaplPlot.dataLineStyle.mutableCopy(); 
lineStyle.lineColor = aaplColor; 

的问题是我得到了我的代码斯威夫特版本说

编译错误

"cannot assign to 'lineColor' in 'lineStyle'". 

我也得到警告说，

"variable lineStyle inferred to have type 'AnyObject', which may be unexpected" 

'applePlot'，顺便说一下，是的ObjectiveC这样定义的类型CPTLineStyle的：

@interface CPTLineStyle : NSObject<NSCoding, NSCopying, NSMutableCopying> 

@property (nonatomic, readonly) CGLineCap lineCap; 
@property (nonatomic, readonly) CGLineJoin lineJoin; 
@property (nonatomic, readonly) CGFloat miterLimit; 
@property (nonatomic, readonly) CGFloat lineWidth; 
@property (nonatomic, readonly) NSArray *dashPattern; 
@property (nonatomic, readonly) CGFloat patternPhase; 
@property (nonatomic, readonly) CPTColor *lineColor; 
@property (nonatomic, readonly) CPTFill *lineFill; 
@property (nonatomic, readonly) CPTGradient *lineGradient; 
@property (nonatomic, readonly, getter = isOpaque) BOOL opaque; 

/// @name Factory Methods 
/// @{ 
+(instancetype)lineStyle; 
/// @} 

/// @name Drawing 
/// @{ 
-(void)setLineStyleInContext:(CGContextRef)context; 
-(void)strokePathInContext:(CGContextRef)context; 
-(void)strokeRect:(CGRect)rect inContext:(CGContextRef)context; 
/// @} 

@end 

任何机构可以告诉我，如果我做错了什么？我如何正确地重写那些代码行？

感谢

Answer 1

的问题是，mutableCopy返回AnyObject。一个AnyObject没有属性，所以你不能分配到它的属性。您需要将其转换为CPTMutableLineStyle。

var lineStyle = aaplPlot.dataLineStyle.mutableCopy() as CPTMutableLineStyle 
lineStyle.lineColor = aaplColor;