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Martin Hope
ValExi
Asked: 2025-04-28 17:51:10 +0800 CST
  • 7

在 C++ 中，为什么派生类不能不使用范围解析运算符而直接显式地调用其基类的析构函数？

我听说在C++中，所有的析构函数都会被编译器处理成“destructor”，也就是说基类和派生类的析构函数同名，从而导致重定义（隐藏）。

这是正确的吗？

#include <iostream>
 
struct base {
    base() { std::cout << "base default \n"; }
    ~base() { std::cout << "~base \n"; }
};
 
struct derived : base {
    derived() { std::cout << "derived default \n"; }
    ~derived()
    {
        //~base();No
        base::~base();
        std::cout << "~derived \n";
    }
};

我知道在实践中几乎没有必要这样做，我只是想了解原理......

c++
Martin Hope
cluster1
Asked: 2025-04-28 17:41:47 +0800 CST
  • 7

我尝试熟悉 Swift 并发，尤其是 MainActor。

我为自己制作了这个演示课程：

@MainActor
class ThreadsDemo {
  let range1000 = 0.. < 1000
  var randomNumber = 0

  init() {
    randomNumber = Int.random(in: range1000)
  }

  func modifyRandomNumber() async {
    print("2. isMain: \(Thread.isMainThread)")
    let newRandomNumber = Int.random(in: range1000)
    print("Generated random-number -> \(newRandomNumber)")
    Timer.scheduledTimer(withTimeInterval: 3.0, repeats: false) {
      _ in
        print("4. isMain (within wait): \(Thread.isMainThread)")
    }
    print("5. isMain: \(Thread.isMainThread)")
    randomNumber = newRandomNumber
  }
}

调用ThreadDemo方法：

.task {
  print("1. isMain: \(Thread.isMainThread)")
  print("Initial random-number -> \(threadsDemo.randomNumber)")
  await threadsDemo.modifyRandomNumber()
  print("Modified random-number -> \(threadsDemo.randomNumber)")
  print("6. isMain: \(Thread.isMainThread)")
}

结果：

1. isMain: true
Initial random-number -> 455
2. isMain: true
Generated random-number -> 578
5. isMain: true
Modified random-number -> 578
6. isMain: true
4. isMain (within wait): true

显然，所有东西都在主线程上运行，甚至是预定计时器内的块。

我很困惑，因为我认为它会使用后台线程来防止 UI 冻结和无响应。

如果它无论如何都在主线程上运行所有内容，那么使用任务的目的是什么？

但我真正想弄清楚的是：

@MainActor 注释是否会导致在主线程上运行所有内容（所有可执行代码）还是只会导致始终在主线程上对状态（分配等）进行更改？

swift
Martin Hope
DeepDish
Asked: 2025-04-28 17:40:50 +0800 CST
  • 5

使用 Entity Framework Core 6（没有迁移，SQL Server 数据库）保存实体时遇到问题。

即使使用外键的明确映射，EF Core 仍会尝试插入表中不存在的列（PecaIdPeca），从而导致 SQL 错误。

模型：

public class OrcamentoPeca
{
    [Key]
    [Column("ID_OrcamentoPeca")]
    public int IdOrcamentoPeca { get; set; }

    [Column("ID_Orcamento")]
    public int IdOrcamento { get; set; }

    [Column("ID_Peca")]
    public int IdPeca { get; set; }

    [Column("Quantidade")]
    public int Quantidade { get; set; }

    // Propriedades de navegação (sem [ForeignKey] attribute)
    public virtual Orcamento Orcamento { get; set; }
    public virtual Peca Peca { get; set; }
}

插入方法：

[HttpPost]
public async Task<IActionResult> SalvarPecasSelecionadas(int IdOrcamento, List<int> PecasSelecionadas, Dictionary<int, int> Quantidades)
{
    foreach (var pecaId in PecasSelecionadas)
    {
        var quantidade = Quantidades.ContainsKey(pecaId) ? Quantidades[pecaId] : 0;

        if (quantidade > 0)
        {
            var orcamentoPeca = new OrcamentoPeca
            {
                IdOrcamento = IdOrcamento,
                IdPeca = pecaId,
                Quantidade = quantidade
            };

            _context.OrcamentoPeca.Add(orcamentoPeca);

            var peca = _context.Pecas.FirstOrDefault(p => p.IdPeca == pecaId);

            if (peca != null)
                peca.Stock -= quantidade;
        }
    }

    await _context.SaveChangesAsync();

    return RedirectToAction("DetalhesOrcamento", new { id = IdOrcamento });
}

数据库上下文：

modelBuilder.Entity<OrcamentoPeca>(entity =>
{
    entity.HasKey(e => e.IdOrcamentoPeca);
    entity.ToTable("OrcamentoPeca");
    entity.Property(e => e.IdOrcamentoPeca).HasColumnName("ID_OrcamentoPeca");
    entity.Property(e => e.IdOrcamento).HasColumnName("ID_Orcamento");
    entity.Property(e => e.IdPeca).HasColumnName("ID_Peca");
    entity.Property(e => e.Quantidade).HasColumnName("Quantidade");

    entity.HasOne(e => e.Orcamento)
        .WithMany(o => o.OrcamentoPecas)
        .HasForeignKey(e => e.IdOrcamento)
        .OnDelete(DeleteBehavior.Cascade);

    entity.HasOne(e => e.Peca)
        .WithMany()
        .HasForeignKey(e => e.IdPeca)
        .OnDelete(DeleteBehavior.Cascade);
});

错误：

SqlException：列名“PecaIdPeca”无效。Microsoft.Data.SqlClient.SqlCommand+<>c.b__211_0（任务结果）

DbUpdateException：保存实体更改时发生错误。有关详情，请参阅内部异常。

Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync（IRelationalConnection 连接，CancellationToken 取消令牌）

生成的SQL代码：

INSERT INTO [OrcamentoPeca] ([ID_Orcamento], [ID_Peca], [PecaIdPeca], [Quantidade])
OUTPUT INSERTED.[ID_OrcamentoPeca]
VALUES (@p0, @p1, @p2, @p3);

中的映射DbContext是正确的，该列PecaIdPeca在数据库中不存在，我已经清理并重建了该项目。

任何帮助都将不胜感激。

c#
Martin Hope
Free Palestine
Asked: 2025-04-28 17:29:59 +0800 CST
  • 6

我想使用其中一个内置微调器，dcc.Loading但在微调器/加载器处于活动状态时在其下方添加一些文本。

import time
import plotly.express as px
import dash_mantine_components as dmc
import dash
from dash import dcc, callback, Output, Input

dash.register_page(module=__name__)

layout = dmc.MantineProvider(
    children=[
        dmc.Select(
            id="dropdown",
            data=["bar", "scatter", "none"],
            value="bar",
        ),
        dcc.Loading(
            type="graph",
            children=dmc.Box(id="my_figure")
        )
    ]
)


@callback(
    Output("my_figure", "children"),
    Input("dropdown", "value")
)
def show_fig(value):
    if value == "bar":
        time.sleep(5)
        return dcc.Graph(figure=px.bar())
    elif value == "scatter":
        time.sleep(5)
        return dcc.Graph(figure=px.scatter())
    else:
        return []

这段代码只会显示“图形”旋转器，没有任何文本。我可以不使用参数向内置旋转器添加文本吗custom_spinner？还是我必须重新创建内置旋转器，添加文本，然后将其传递给custom_spinner？

python
Martin Hope
Matty
Asked: 2025-04-28 17:25:27 +0800 CST
  • 4

我正在尝试创建自定义 WAF 规则以允许流量到特定的 URI - 此部署是通过 Terraform 完成的。

我收到的错误是：

Application Gateway Web Application Firewall Policy Name: "waf-policy-prod-uksouth"): unexpected status 400 (400 Bad Request) with error: ApplicationGatewayFirewallMatchValueNoCollection: Custom Rule 'AllowAmexPay' does not have a valid collection match variable 'RequestUri' which support selector in its condition in context 'properties.customRules[2].matchConditions[0].matchVariables[0]'.
│ 
│   with azurerm_web_application_firewall_policy.waf_policy,
│   on application_gw.tf line 224, in resource "azurerm_web_application_firewall_policy" "waf_policy":
│  224: resource "azurerm_web_application_firewall_policy" "waf_policy" {

TFVars 文件：

custom_rules = [
    {
        name                    = "RecitePreferences"
        priority                = "70"
        enabled                 = true
        rule_type               = "MatchRule"
        variable_name           = "RequestCookies"
        selector                = "Recite.Preferences"
        operator                = "Any"
        action                  = "Allow"
    },
        {
        name                    = "CookieConsent"
        priority                = "71"
        enabled                 = true
        rule_type               = "MatchRule"
        variable_name           = "RequestCookies"
        selector                = "CookieConsent"
        operator                = "Any"
        action                  = "Allow"
    },
        {
        name                    = "AllowAmexPay"
        priority                = "80"
        enabled                 = true
        rule_type               = "MatchRule"
        variable_name           = "RequestUri"
        selector                = "/smart-card/amex-pay"
        operator                = "Contains"
        action                  = "Allow"
    },
        {
        name                    = "AllowAmexPayComplete"
        priority                = "81"
        enabled                 = true
        rule_type               = "MatchRule"
        variable_name           = "RequestUri"
        selector                = "/smart-card/amex-pay-complete"
        operator                = "Contains"
        action                  = "Allow"
    }
]

Variables.tf 文件：

variable "custom_rules" {
  type  = list(object({
    name                    = string
    priority                = string
    enabled                 = bool
    rule_type               = string
    variable_name           = string
    operator                = string
    selector                = string
    action                  = string
  }))
}

应用程序网关配置：

resource "azurerm_web_application_firewall_policy" "waf_policy" {
  name                = "waf-policy-${var.general_environment}-${var.general_location}"
  resource_group_name = azurerm_resource_group.prod.name
  location            = azurerm_resource_group.prod.location

  policy_settings {
    enabled                     = true
    mode                        = "Detection"
    request_body_check          = false
    file_upload_limit_in_mb     = 100
    max_request_body_size_in_kb = 128
  }
  managed_rules {
    managed_rule_set {
      type    = "OWASP"
      version = "3.2"
      
      dynamic "rule_group_override" {
        for_each = var.rule_group_override
        content {
          rule_group_name = rule_group_override.key

          dynamic "rule" {
            for_each = rule_group_override.value
            content {
            id      = rule.value.id
            enabled = rule.value.enabled
          } 
        }
      }
    }
  }

    dynamic "exclusion" {
      for_each = var.exclusion

      content {
        match_variable          = exclusion.value["match_variable"]
        selector                = exclusion.value["selector"]
        selector_match_operator = exclusion.value["selector_match_operator"]
      }
    }
    managed_rule_set {
      type = "Microsoft_BotManagerRuleSet"
      version = "1.0"
    }
  }
    dynamic "custom_rules" {
      for_each = var.custom_rules

      content {
          name          = custom_rules.value["name"]
          enabled       = custom_rules.value["enabled"]
          priority      = custom_rules.value["priority"]
          rule_type     = custom_rules.value["rule_type"]
          action        = custom_rules.value["action"]
          match_conditions {
            operator     = custom_rules.value["operator"]
            match_variables {
              variable_name = custom_rules.value["variable_name"]
              selector      = custom_rules.value["selector"]
            }
          }
        } 
      }     
}

只是想知道是否有不同/更好的方法来传递变量，因为这些变量目前在 Apply 上出错？

Martin Hope
ankit maltare
Asked: 2025-04-28 16:57:15 +0800 CST
  • 5

下面是我的代码，其中 svg 元素内有一个圆圈，我想通过 jinja2 使用 streamlit 中的 st.html 来渲染它，问题是容器可见，但 svg 元素不可见。它是空白的。请参阅下面的代码。

<style>
html,body {
  height: 100%;
  background-color: #404040;
  margin: 0;
  display: flex;
  justify-content: center;
  align-items: center;
}

.container {
  display: flex;
  width: 500px;
  /* Extended width for pipe */
  height: 500px;
  border: 3px solid #EEEEEE;
  justify-content: center;
  align-items: center;
  border-radius: 20px;

}

.drawing {
  position: relative;
  width: 2000px;
  /* Extended width for pipe */
  height: 600px;
}

.circle-svg {
  width: 100%;
  height: 100%;
}

.c3 {
  fill: none;
  stroke: grey;
  stroke-width: 10;
}

</style>
<body>
  <div class="container">
    <div class="drawing">
      <svg viewBox="0 0 500 500" class="circle-svg">
                <!-- Circle -->
                <circle class="c3" cx="250" cy="250" r="198"></circle>
            </svg>
    </div>
  </div>
</body>

Python代码：

def cutting_dimention(html_content):
    # Directly use the HTML content without treating it as a file path
    template = Template(html_content)
    rendered_html = template.render()  # Render the HTML with Jinja2
    st.text(rendered_html)  # Display rendered HTML text
    st.html(rendered_html)  # Display rendered HTML as an HTML block in Streamlit

使用 HTML 内容调用该函数

切割尺寸（我的圆）

python
Martin Hope
Miguel Bartelsman
Asked: 2025-04-28 16:28:23 +0800 CST
  • 2

如果你查看它的实现，ConcurrentDictionary<K,V>你会发现它有一个ICollection<KeyValuePair<K,V>.Add(...)定义为私有的成员。然而，据我理解，接口实现不能标记为私有，而且如果我尝试这样做，编译器也不允许。

这怎么可能呢？

c#
Martin Hope
GrnEyedDvl
Asked: 2025-04-28 16:11:54 +0800 CST
  • 5

这里有一个类似的问题，但答案不起作用，XenForo 的官方答案也不起作用。显然，他们在论坛从 /forums 设置迁移到根域级别时遇到了问题，但修复方法不起作用。

旧链接 https://www.twcenter.net/forums/member.php?10263-Gaius-Baltar

新链接 https://twcenter.net/members/gaius-baltar.10263/

旧链接 https://www.twcenter.net/forums/showthread.php?581961-Name-Change-Requests

新链接 https://twcenter.net/threads/name-change-requests.581961/

这确实对非友好 URL 有效，但我没有很多这样的 URL。

           return 301 /threads/$arg_t/;
        }

        location = /member.php {
           return 301 /members/$arg_u/;
        }

我认为让我困惑的是文本和 ID 之间的切换。在 vBulletin 中，它先 id，再文本

在 XenForo 中它的 the-text.id

nginx
Martin Hope
user30266210
Asked: 2025-04-28 16:06:42 +0800 CST
  • 6

我有一个通用的 DialogueWindow 组件：

function DialogueWindow({elements}) {

  return (

    <div className="backdrop">

      <dialog className="dialogue-window">

        {elements}

      </dialog>

    </div>
  )
}

export default DialogueWindow

它内部会显示所有传递给它的元素。目前我传递了一个 FileUploader 元素，它有一个“取消”按钮，用户可以用它来关闭对话框。

在 App.js 中：

<DialogueWindow
     elements={
        <FileUploader/>
     }
/>

在 FileUploader 中：

function FileUploader() {

  ...

  return (

    <div className="file-uploader">

        ...

        <div className="file-uploader-button-container">

            <button>
                Upload
            </button>

            <button>
                Cancel
            </button>

        </div>

    </div>
  )
}

export default FileUploader

我见过在标准 JavaScript 中调用 document.getElementById() 来获取对话框元素，然后对其调用 close() 方法。但这在 React 中是如何实现的呢？

javascript
Martin Hope
carpediem
Asked: 2025-04-28 15:12:53 +0800 CST
  • 5

我正在尝试使用 matplotlib 和 pyplot 绘制一个包含两个子图的图表来可视化模拟结果。两个图表都应该包含动画：一个使用 NetGraph 库（它是一个包含节点的图表，用于显示网络流量），另一个绘制另外两个变量的线图（为了简单起见，这里使用 sin(x) 和 cos(x)，它们都应该在每个时间段更新——就像图表一样）。我有一个更新函数可以更新图表，但我不确定如何同时更新线图。欢迎大家提出任何建议。

import numpy as np
import matplotlib.pyplot as plt

from matplotlib.animation import FuncAnimation
from netgraph import Graph

# Simulate a dynamic network with
total_frames = 21
total_nodes = 5
NODE_LABELS = {0: 'A', 1: 'B', 2: 'C', 3: 'D', 4: 'E'}
NODE_POS = {0: (0.0, 0.5), 1: (0.65, 0.25), 2: (0.7, 0.5), 3: (0.5, 0.75), 4: (0.25, 0.25)}
adjacency_matrix = np.random.rand(total_nodes, total_nodes) < 0.25
weight_matrix = np.random.randn(total_frames, total_nodes, total_nodes)

# Normalise the weights, such that they are on the interval [0, 1].
vmin, vmax = -2, 2
weight_matrix[weight_matrix<vmin] = vmin
weight_matrix[weight_matrix>vmax] = vmax
weight_matrix -= vmin
weight_matrix /= vmax - vmin

cmap = plt.cm.RdGy

def annotate_axes(fig):
    for i, ax in enumerate(fig.axes):
        ax.tick_params(labelbottom=False, labelleft=False)

fig = plt.figure(figsize=(11, 6))

ax1 = plt.subplot2grid((6, 11), (0, 0), rowspan=6, colspan=5)
ax2 = plt.subplot2grid((6, 11), (1, 6), rowspan=2, colspan=5)

annotate_axes(fig)
title1 = ax1.set_title('Simulation viz', x=0.25, y=1.25)
title2 = ax2.set_title('Flow @t', x=0.15, y=1.25)

g = Graph(adjacency_matrix, node_labels=NODE_LABELS,
            node_layout = NODE_POS, edge_cmap=cmap, arrows=True, ax=ax1)

def update(ii):
    artists = []
    for jj, kk in zip(*np.where(adjacency_matrix)):
        w = weight_matrix[ii, jj, kk]
        artist = g.edge_artists[(jj, kk)]
        artist.set_facecolor(cmap(w))
        artist.update_width(0.03 * np.abs(w-0.5))
        artists.append(artist)
    return artists

animation = FuncAnimation(fig, update, frames=total_frames, interval=200, blit=True, repeat=False)
plt.show()
python
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