- (nullable __kindof UIResponder *)findNextResonderInClass:(nonnull Class)responderClass
{
	UIResponder *next = self;
	do {
		next = [next nextResponder];
		if ([next isKindOfClass:responderClass]) {
		break;
	}
	// next 不为空 且 不是达到最底层的 appdelegate
	} while (next!=nil && ![next conformsToProtocol:@protocol(UIApplicationDelegate)]);
	return next;
}
// 查询响应最近的 controller
UIViewController *vc = [view findNextResonderInClass:[UIViewController class]];

#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
#define WIDTH 10
#define HEIGHT 10
#define DEPTH 10
#define SIZE 100
#define SPACING 150
#define CAMERA_DISTANCE 500
@interface ViewController ()

@property (nonatomic, strong) IBOutlet UIScrollView *scrollView;
@end
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    self.scrollView.contentSize = CGSizeMake((WIDTH - 1)*SPACING, (HEIGHT - 1)*SPACING);
    CATransform3D transform = CATransform3DIdentity;
    transform.m34 = -1.0 / CAMERA_DISTANCE;
    self.scrollView.layer.sublayerTransform = transform;
    for (int z = DEPTH - 1; z >= 0; z--) {
        for (int y = 0; y < HEIGHT; y++) {
            for (int x = 0; x < WIDTH; x++) {
                //create layer
                CALayer *layer = [CALayer layer];
                layer.frame = CGRectMake(0, 0, SIZE, SIZE);
                layer.position = CGPointMake(x*SPACING, y*SPACING);
                layer.zPosition = -z*SPACING;
                //set background color
                layer.backgroundColor = [UIColor colorWithWhite:1-z*(1.0/DEPTH) alpha:1].CGColor;
                //attach to scroll view
                [self.scrollView.layer addSublayer:layer];
            }
        }
    }
}
@end

//
//  ViewController.swift
//  DrawDemo
//
//  Created by XcodeYang on 07/12/2017.
//  Copyright © 2017 XcodeYang. All rights reserved.
//
import UIKit
let numberOfDrawer = 30
let drawColor = UIColor.yellow
let lineWidth: CGFloat = 1.0
enum PenType: String {
	case pencil = "铅笔"
	case bucket = "水桶"
	case eraser = "橡皮擦"
	mutating func next() {
		switch self {
		case .pencil:
			self = .bucket
		case .bucket:
			self = .eraser
		case .eraser:
			self = .pencil
		}
	}
}
class ViewController: UIViewController {
	
	var pentype = PenType.pencil
	var drawLayer: CAShapeLayer!
	var drawPaths = [CGMutablePath]()
	@IBOutlet weak var penButton: UIButton!
	
	var historyAllRecords = [CAShapeLayer]()
	var historyShowingRecords = [CAShapeLayer]()
	
	private func creatNewLayer()-> CAShapeLayer {
		let layer = CAShapeLayer()
		layer.lineWidth = lineWidth;
		layer.strokeColor = drawColor.cgColor
		layer.fillColor = penButton.isSelected ? drawColor.cgColor : UIColor.clear.cgColor
		view.layer.addSublayer(layer)
		return layer
	}
	override func viewDidLoad() {
		super.viewDidLoad()
		
	}
	
	override var prefersStatusBarHidden: Bool {
		return true
	}
	
	override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
		if pentype == .eraser { return }
		
		drawPaths.removeAll()
		drawLayer = creatNewLayer()
		guard let point = touches.first?.location(in: view) else { return }
		(0...numberOfDrawer).forEach { index in
			let path = CGMutablePath()
			path.move(to: convertPointByCenterOfPoint(point: point, index: index))
			drawPaths.append(path)
		}
	}
	
	override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
		
		guard let point = touches.first?.location(in: view) else { return }
		if pentype == .eraser {
			let deleteLayers = historyShowingRecords.filter({ (pathLayer) -> Bool in
				return pathLayer.path!.contains(point)
			})
			deleteLayers.forEach{ $0.removeFromSuperlayer() }
			return
		}
		
		drawPaths.enumerated().forEach { (index, path) in
			path.addLine(to: convertPointByCenterOfPoint(point: point, index: index))
		}
		
		if pentype == .bucket {
			let resultPath = drawPaths.reduce(CGMutablePath(), { (resultPath, nextPath) -> CGMutablePath in
				let newNext = nextPath.mutableCopy()
				newNext?.closeSubpath()
				resultPath.addPath(newNext!)
				return resultPath
			})
			drawLayer.path = resultPath
		} else {
			let resultPath = drawPaths.reduce(CGMutablePath(), { (resultPath, nextPath) -> CGMutablePath in
				resultPath.addPath(nextPath)
				return resultPath
			})
			drawLayer.path = resultPath
		}
	}
	
	override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
		if pentype == .eraser { return }
		historyShowingRecords.append(drawLayer)
		historyAllRecords = historyShowingRecords
	}
	
	override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
		if pentype == .eraser { return }
		historyShowingRecords.append(drawLayer)
		historyAllRecords = historyShowingRecords
	}
	
	@IBAction func penChange(_ sender: UIButton) {
		pentype.next()
		sender.setTitle(pentype.rawValue, for: .normal)
	}
	
	@IBAction func backAction(_ sender: UIButton) {
		if let deleteLayer = historyShowingRecords.last {
			deleteLayer.removeFromSuperlayer()
			historyShowingRecords.removeLast()
		}
	}
	
	@IBAction func recoverAction(_ sender: Any) {
		if historyShowingRecords.count < historyAllRecords.count {
			let recoverLayer = historyAllRecords[historyShowingRecords.count]
			historyShowingRecords.append(recoverLayer)
			view.layer.addSublayer(recoverLayer)
		}
	}
	
	@IBAction func cleanAction(_ sender: Any) {
		historyShowingRecords.forEach{ $0.removeFromSuperlayer() }
		historyShowingRecords.removeAll()
		historyAllRecords.removeAll()
	}
}
extension ViewController {
	
	func convertPointByCenterOfPoint(point:CGPoint, index:Int) -> CGPoint {
		let center = CGPoint(x:view.bounds.width/2.0, y:view.bounds.height/2.0)
		let increaseAngle = Double.pi * 2.0 * Double(index) / Double(numberOfDrawer);
		let radius: Double = sqrt(pow(Double(point.x) - Double(center.x), 2) + pow(Double(point.y) - Double(center.y), 2))
		let angle: Double = getAngle(startPoint: center, endPoint: point) + increaseAngle
		return CGPoint(x: cos(angle) * radius + Double(center.x), y: sin(angle)*radius + Double(center.y))
	}
	
	func getAngle(startPoint:CGPoint, endPoint:CGPoint) -> Double {
		let y = Double(endPoint.y - startPoint.y)
		let x = Double(endPoint.x - startPoint.x)
		let length = sqrt(y*y + x*x)
		var rads = asin(y/length)
		
		if x < 0 {
			rads = (Double.pi - rads)
		}
		return rads
	}
}

NSDictionary *viewsDictionary = [NSDictionary dictionaryWithObjectsAndKeys:label1,@"label1",label2,@"label2",label3,@"label3",label4,@"label4", nil];
NSDictionary *metrics = [NSDictionary dictionaryWithObject:@(88) forKey:@"labelHeight"];
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[label1(labelHeight)]-[label2(labelHeight)]-[label3(labelHeight)]-[label4(labelHeight)]-(>=10)-|" options:NSLayoutFormatAlignAllLeft metrics:metrics views:viewsDictionary];
[view addConstraints:constraints];

view.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint * constraint = [NSLayoutConstraint
                                       constraintWithItem:view             
                                       attribute:NSLayoutAttributeTop          
                                       relatedBy:NSLayoutRelationEqual          
                                       toItem:view                       
                                       attribute:NSLayoutAttributeTop           
                                       multiplier:1.0                      
                                       constant:10];                            
[view addConstraint:constraint];

//iOS8
[NSLayoutConstraint constraintWithItem:view1 attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:view2 attribute:NSLayoutAttributeCenterX multiplier:1 constant:10];
//iOS9
view.translatesAutoresizingMaskIntoConstraints = NO;
[view.widthAnchor constraintEqualToConstant:100];
[view.heightAnchor constraintEqualToConstant:100];
[view.centerXAnchor constraintEqualToAnchor:view1.centerXAnchor];
[view.centerYAnchor constraintEqualToAnchor:view1.centerYAnchor];

[view mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(@(10));
}];

[view mas_makeConstraints:^(MASConstraintMaker *make) {
    make.top.equalTo(@(10));
    make.left.equalTo(@(10));
    make.bottom.equalTo(@(-10));
    make.right.equalTo(@(-10));
}];

/**
 *  Finds the closest common superview between this view and another view
 *
 *  @param  view    other view
 *
 *  @return returns nil if common superview could not be found
 */
- (instancetype)mas_closestCommonSuperview:(MAS_VIEW *)view;
/**
 *  Creates a MASConstraintMaker with the callee view.
 *  Any constraints defined are added to the view or the appropriate superview once the block has finished executing
 *
 *  @param block scope within which you can build up the constraints which you wish to apply to the view.
 *
 *  @return Array of created MASConstraints
 */
- (NSArray *)mas_makeConstraints:(MASConstraintMakerConfigBlock)block;
/**
 *  Creates a MASConstraintMaker with the callee view.
 *  Any constraints defined are added to the view or the appropriate superview once the block has finished executing.
 *  If an existing constraint exists then it will be updated instead.
 *
 *  @param block scope within which you can build up the constraints which you wish to apply to the view.
 *
 *  @return Array of created/updated MASConstraints
 */
- (NSArray *)mas_updateConstraints:(MASConstraintMakerConfigBlock)block;
/**
 *  Creates a MASConstraintMaker with the callee view.
 *  Any constraints defined are added to the view or the appropriate superview once the block has finished executing.
 *  All constraints previously installed for the view will be removed.
 *
 *  @param block scope within which you can build up the constraints which you wish to apply to the view.
 *
 *  @return Array of created/updated MASConstraints
 */
- (NSArray *)mas_remakeConstraints:(MASConstraintMakerConfigBlock)block;

view.top.left.equalTo(superView).offset(10);

class ClassB;
interface ClassA : NSObject
// 1. 定义一些 block 属性
property(nonatomic, readonly) ClassA *(^aaa)(BOOL enable);
property(nonatomic, readonly) ClassA *(^bbb)(NSString* str);
@property(nonatomic, readonly) ClassB *(^ccc)(NSString* str);
@implement ClassA
// 2. 实现这些 block 方法，block 返回值类型很关键，影响着下一个链式
- (ClassA *(^)(BOOL))aaa
{
    return ^(BOOL enable) {
        //code
        if (enable) {
            NSLog(@"ClassA yes");
        } else {
            NSLog(@"ClassA no");
        }
        return self;
    }
}
- (ClassA *(^)(NSString *))bbb
{
    return ^(NSString *str)) {
        //code
        NSLog(@"%@", str);
        return self;
    }
}
// 这里返回了ClassB的一个实例，于是后面就可以继续链式 ClassB 的 block 方法
// 见下面例子 .ccc(@"Objective-C").ddd(NO)
- (ClassB * (^)(NSString *))ccc
{
    return ^(NSString *str) {
        //code
        NSLog(@"%@", str);
        ClassB* b = [[ClassB alloc] initWithString:ccc];
        return b;
    }
}
//------------------------------------------
@interface ClassB : NSObject
@property(nonatomic, readonly) ClassB *(^ddd)(BOOL enable);
- (id)initWithString:(NSString *)str;
@implement ClassB
- (ClassB *(^)(BOOL))ddd
{
    return ^(BOOL enable) {
        //code
        if (enable) {
            NSLog(@"ClassB yes");
        } else {
            NSLog(@"ClassB no");
        }
        return self;
    }
}
// 最后我们可以这样做
id a = [ClassA new];
a.aaa(YES).bbb(@"HelloWorld!").ccc(@"Objective-C").ddd(NO)

- (MASConstraint * (^)(CGFloat))offset {
    return ^id(CGFloat offset){
        self.offset = offset;
        return self;
    };
}