小编Vat*_*not的帖子

/// Destroy the object the pointer points to.
///
/// Precondition: the memory is initialized.
///
/// Postcondition: the value has been destroyed and the memory must
/// be initialized before being used again.
func destroy()

什么条款object,memory并value在这方面是什么意思？

我正在运行Xcode 6.3,而我正在使用card.io的iOS SDK 5.2.0.

这是错误:

重复符号_llvm.cmdline:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master /CardIO/libCardIO.a(CardIOPostalCodeTextFieldDelegate.o)复制符号_llvm.embedded.module:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/ Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOPostalCodeTextFieldDelegate.o)复制符号_llvm.cmdline in:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/ libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOConfig.o)复制符号_llvm.embedded.module in:/ Users/comcubatormica/Downloads /卡.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOConfig.o)重复符号_llvm.cmdline in:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO. a(CardIOView.o)重复符号_llvm.embedded.module位于:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/ Users/comcubatormica/Downloads/card .io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)ld:64个用于体系结构x86_64 clang的重复符号:错误:链接器命令失败,退出代码为1(使用-v查看调用)io-iOS-SDK-master/CardIO/libCardIO.a(CardIOConfig.o)复制符号_llvm.cmdline:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell. o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)复制符号_llvm.embedded.module:/Users/comcubatormica/Downloads/card.io-iOS -SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)ld:64个重复符号用于体系结构x86_64 clang:错误:链接器命令失败,退出代码为1(使用-v查看调用)io-iOS-SDK-master/CardIO/libCardIO.a(CardIOConfig.o)复制符号_llvm.cmdline:/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOTableViewCell. o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)复制符号_llvm.embedded.module:/Users/comcubatormica/Downloads/card.io-iOS -SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)ld:64个重复符号用于体系结构x86_64 clang:错误:链接器命令失败,退出代码为1(使用-v查看调用)o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)复制符号_llvm.embedded.module:/Users/comcubatormica/Downloads/card.io-iOS -SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)ld:64个重复符号用于体系结构x86_64 clang:错误:链接器命令失败,退出代码为1(使用-v查看调用)o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)复制符号_llvm.embedded.module:/Users/comcubatormica/Downloads/card.io-iOS -SDK-master/CardIO/libCardIO.a(CardIOTableViewCell.o)/Users/comcubatormica/Downloads/card.io-iOS-SDK-master/CardIO/libCardIO.a(CardIOView.o)ld:64个重复符号用于体系结构x86_64 clang:错误:链接器命令失败,退出代码为1(使用-v查看调用)链接器命令失败,退出代码为1(使用-v查看调用)链接器命令失败,退出代码为1(使用-v查看调用)

我怎么解决这个问题？

一张图片似乎比一个令人困惑的标题更好:

我已将我的主应用程序复制到不同的目标.我还设法productnam在目标的Build Settings下更改了e.我看到我的(Productname)改变影响了Bundle ID,所以我想这没关系.

现在我该如何更改方案的名称？

在本地范围之外声明的变量仍在范围内可用/可访问.因此,我想如果我重新声明范围内的变量,编译器会告诉我重新声明错误.

在以下代码片段中,常量tipPercentage在if范围之外声明,并在if范围内设置

let totallBill = 95.00
let tipPercentage: Double
let rating = 3

if rating == 5 {
    tipPercentage = 0.25
} else if rating >= 3 {
    tipPercentage = 0.15
} else {
    let tipPercentage = 0.10 //# error caused by the let
}

let totalPaid = totallBill + totallBill * tipPercentage

问题

我在if范围内重新声明了常量.我认为它会告诉重新声明变量错误,但相反,它给出了" constant "tipPercentage" used before being initialized." 为什么会这样？

非常感谢

以下内容应该创建一个Text边界，该边界占据整个屏幕，但似乎什么也没做。

struct ContentView: View {
    var body: some View {
        Text("foo")
            .relativeSize(width: 1.0, height: 1.0)
            .background(Color.red)
    }
}

以下黑客：

extension View {
    /// Causes the view to fill into its superview.
    public func _fill(alignment: Alignment = .center) -> some View {
        GeometryReader { geometry in
            return self.frame(
                width: geometry.size.width,
                height: geometry.size.height,
                alignment: alignment
            )
        }
    }
}

struct ContentView2: View {
    var body: some View {
        Text("foo")
            ._fill()
            .background(Color.red)
    }
}

似乎工作。

这是带有的SwiftUI错误relativeSize，还是我缺少某些东西？

我正在为iOS和Android开发WiFi扫描仪应用程序.

现在我发现Apple不允许在iOS应用程序中使用他们的WiFi扫描仪API页面.

这种限制的实际原因是什么？Apple正式发表评论吗？另外,有任何变通方法吗？

我正在制作一个包含模板和类的动态数组.

这是我遇到问题的代码:

template<typename GType>
class GArray
{
   GType* array_type = nullptr;
   int size = 0;

public:
GArray(GType Size)
{
    size = Size;
    array_type = new GType[size];

    for (int i = 0; i < size; i++)
        array_type[i] = NULL;
}

void Push(GType Item)
{
    size++;

    GType* temp = new GType[size];

    for (int i = 0; i < size-1; i++)
        temp[i] = array_type[i];

    temp[size] = Item;

    delete[] array_type;
    array_type = temp;
    temp = nullptr;
}

GType& operator[] (int Index)
{
    if (Index …