我有一个包含const 2d数组值的类，我想在调用构造函数时定义这个数组。我被告知在const上使用永远不应该更改的值是首选，所以我想在这种情况下尝试。
class A {
public:
A(const int passedArray[2][2]) : memberArray(passedArray) {}
private:
const int memberArray[2][2];
};
const int passedArray[][2] = {
{0,0},
{0,1}
};
A a(passedArray); // fails with "incompatible types
//in assignment of 'const int (*)[2]' to 'const in[2][2]'
A a(&passedArray); // fails
const int passedArray[2][2] = ...，private: const int** memberArray等
我知道我必须使用初始化列表，因为构造函数不能更改const的值。这在C ++ 11上是否可行？
答案 0 :(得分：0)
对您的问题的评论有一些很好的信息。
之后是工作代码：
/*
ManagePages - This section handles the UIScrollView
*/
private func managePages()
{
self.sideScrollView.frame = CGRect(x:0, y:0, width:self.view.frame.width, height:self.view.frame.height)
let scrollViewWidth:CGFloat = self.sideScrollView.frame.width
let scrollViewHeight:CGFloat = self.sideScrollView.frame.height
let imgOne = UIImageView(frame: CGRect(x:(scrollViewWidth/2) - (129/2), y:157,width:129, height:84))
imgOne.image = UIImage(named: "Image1")
imgOne.contentMode = .scaleAspectFit
let imgTwo = UIImageView(frame: CGRect(x:((((scrollViewWidth*2)/4))*3)-(153/2), y:137,width:153, height:153))
imgTwo.image = UIImage(named: "Image2")
imgOne.contentMode = .scaleAspectFit
let imgThree = UIImageView(frame: CGRect(x:((((scrollViewWidth*3)/6))*5)-(132/2), y:137,width:132, height:151))
imgThree.image = UIImage(named: "Image3")
imgOne.contentMode = .scaleAspectFit
let imgFour = UIImageView(frame: CGRect(x:((((scrollViewWidth*4)/8))*7)-(139/2), y:137,width:139, height:118))
imgFour.image = UIImage(named: "Image4")
imgOne.contentMode = .center
let imgFive = UIImageView(frame: CGRect(x:((((scrollViewWidth*5)/10))*9)-(171/2), y:127,width:171, height:169))
imgFive.image = UIImage(named: "Image5")
imgOne.contentMode = .scaleAspectFit
let imgSix = UIImageView(frame: CGRect(x:((((scrollViewWidth*6)/12))*11)-(133/2), y:127,width:133, height:175))
imgSix.image = UIImage(named: "Image6")
imgSix.contentMode = .scaleAspectFit
let messageOne = UIImageView(frame: CGRect(x: 0, y: (137+153+25), width: scrollViewWidth, height: 112))
messageOne.image = UIImage(named: "Message1")
messageOne.contentMode = .scaleAspectFit
let titleOne = UIImageView(frame: CGRect(x: (scrollViewWidth/2) - (131/2), y:57, width: 131, height: 56))
titleOne.image = UIImage(named: "Title1")
titleOne.contentMode = .scaleAspectFit
let titleTwo = UIImageView(frame: CGRect(x:(((scrollViewWidth*2)/4)*3)-(184/2), y: 57, width:184, height: 56))
titleTwo.image = UIImage(named: "Title2")
titleTwo.contentMode = .scaleAspectFit
let titleThree = UIImageView(frame: CGRect(x:(((scrollViewWidth*3)/6)*5)-(227/2), y: 57, width:227, height: 56))
titleThree.image = UIImage(named: "Title3")
titleThree.contentMode = .scaleAspectFit
let titleFour = UIImageView(frame: CGRect(x:(((scrollViewWidth*4)/8)*7)-(scrollViewWidth/2), y: 57, width:scrollViewWidth, height: 56))
titleFour.image = UIImage(named: "Title4")
titleFour.contentMode = .scaleAspectFit
let titleFive = UIImageView(frame: CGRect(x:(((scrollViewWidth*5)/10)*9)-(270/2), y: 57, width:270, height: 56))
titleFive.image = UIImage(named: "Title5")
titleFive.contentMode = .scaleAspectFit
let titleSix = UIImageView(frame: CGRect(x:(((scrollViewWidth*6)/12)*11)-(270/2), y: 57, width:270, height: 56))
titleSix.image = UIImage(named: "Title6")
titleSix.contentMode = .scaleAspectFit
for (index,element) in inputFields.enumerated()
{
if(index == 0)
{
element.frame = CGRect(x: calculateTextFieldXLocation(pageNumber: 1, scrollWidth: scrollViewWidth, width: 244), y: 222, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.keyboardType = .emailAddress
element.autocapitalizationType = .none
element.placeholder = "Email"
element.contentMode = .scaleAspectFit
}
else if(index == 1)
{
element.frame = CGRect(x: calculateTextFieldXLocation(pageNumber: 1, scrollWidth: scrollViewWidth, width: 244), y: 327, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.isSecureTextEntry = true
element.placeholder = "Password"
element.contentMode = .scaleAspectFit
element.returnKeyType = .done
}
else if(index == 2)
{
element.frame = CGRect(x: calculateTextFieldXLocation(pageNumber: 2, scrollWidth: scrollViewWidth, width: 244), y: 222, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "First Name"
element.contentMode = .scaleAspectFit
element.returnKeyType = .done
}
else if(index == 3)
{
element.frame = CGRect(x: calculateTextFieldXLocation(pageNumber: 2, scrollWidth: scrollViewWidth, width: 244), y: 327, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Last Name"
element.contentMode = .scaleAspectFit
element.returnKeyType = .done
}
else if(index == 4)
{
element.frame = CGRect(x: (scrollViewWidth*3)-(scrollViewWidth/2)-(122), y: 432, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Date of Birth"
element.contentMode = .scaleAspectFit
addDatePicker(element: element)
}
else if(index == 5)
{
element.frame = CGRect(x: (scrollViewWidth*3)-(scrollViewWidth/2)-(122), y: 534, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Gender"
element.contentMode = .scaleAspectFit
element.inputView = genderPicker
}
else if(index == 6)
{
element.frame = CGRect(x: (scrollViewWidth*4)-(scrollViewWidth/2)-(122), y: 222, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Favorite Type"
element.contentMode = .scaleAspectFit
element.inputView = typePicker
}
else if(index == 7)
{
element.frame = CGRect(x: (scrollViewWidth*4)-(scrollViewWidth/2)-(122), y: 327, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Eye Color"
element.contentMode = .scaleAspectFit
element.inputView = colorPicker
}
else if(index == 8)
{
element.frame = CGRect(x: (scrollViewWidth*4)-(scrollViewWidth/2)-(122), y: 432, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Height"
element.contentMode = .scaleAspectFit
element.returnKeyType = .done
}
else if(index == 9)
{
element.frame = CGRect(x: (scrollViewWidth*4)-(scrollViewWidth/2)-(122), y: 534, width: 244, height: 49)
element.background = UIImage(named:"SetupTextField")
element.font = UIFont(name: "System", size: 24.0)
element.textAlignment = .center
element.placeholder = "Weight"
element.contentMode = .scaleAspectFit
element.keyboardType = .decimalPad
element.returnKeyType = .done
}
}
let swipeArrow = UIImageView(frame: CGRect(x:(scrollViewWidth/2)-(170/2), y: scrollViewHeight-120, width:170, height: 60))
swipeArrow.image = UIImage(named: "WelcomeSwipeToContinue")
swipeArrow.contentMode = .scaleAspectFit
let getStartedButton = UIButton(frame: CGRect(x:((scrollViewWidth*5) + scrollViewWidth/2)-125, y: scrollViewHeight-175, width: 250, height: 99))
getStartedButton.setImage(UIImage(named: "GetStartedButton"), for: UIControlState.normal)
getStartedButton.addTarget(self, action: #selector(finishSetup), for: .touchUpInside)
self.sideScrollView.addSubview(imgOne)
self.sideScrollView.addSubview(messageOne)
self.sideScrollView.addSubview(titleOne)
self.sideScrollView.addSubview(titleTwo)
self.sideScrollView.addSubview(titleThree)
self.sideScrollView.addSubview(titleFour)
self.sideScrollView.addSubview(titleFive)
self.sideScrollView.addSubview(titleSix)
self.sideScrollView.addSubview(swipeArrow)
for fieldName in inputFields
{
self.sideScrollView.addSubview(fieldName)
}
self.sideScrollView.addSubview(getStartedButton)
self.sideScrollView.contentSize = CGSize(width:self.sideScrollView.frame.width * 6, height:self.sideScrollView.frame.height)
self.sideScrollView.delegate = self
//self.pageControl.currentPage = 0
}
如果您的业务需要在您的班级中拥有“const多维数组” 你必须采取以下任何一种方式。
//g++ 5.4.0
#include <iostream>
class A {
public:
A(int passedArray[2][2])
{
//USE STD COPY TO COPY THE ARRAYS.
std::copy(&passedArray[0][0], &passedArray[0][0]+4,&memberArray[0][0]);
//PRINT VALUES TO TEST
for (int i = 0; i < 2; i++)
{
for (int j = 0; j < 2; j++)
{
std::cout << memberArray[i][j] << std::endl;
}
}
}
private:
int memberArray[2][2];
};
int main()
{
//INITIALIZE YOUR ARRAY
int passedArray[2][2] = {
{0,0},
{0,1}
};
//CREATE OBJECT
A a(passedArray);
}
OR
class A {
public:
A(const int passedArray[2][2])
{
}
private:
const int memberArray[2][2] = {{5,6},{7,8}}; //INITIALIZE HERE
};