iOS CALayer-实现颜色的渐变和曲线图

最近研究了一下颜色的渐变

效果，下面简单抽出一个类的代码，方便查看：

#import <UIKit/UIKit.h>

@interface YXLayerView : UIView
{
    CAShapeLayer * _lineLayer,* _maskLayer;
    CAGradientLayer * _backgroundLayer;
}

@end

#import "YXLayerView.h"

@implementation YXLayerView

- (instancetype)init
{
    self = [super init];
    if (self) {
        [self inits];
    }
    return self;
}

- (instancetype)initWithCoder:(NSCoder *)coder
{
    self = [super initWithCoder:coder];
    if (self) {
        [self inits];
    }
    return self;
}

- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self inits];
    }
    return self;
}

- (void)inits
{
    self.backgroundColor = [UIColor grayColor];
    self.clipsToBounds &