我使用SQLdatareader从数据库构建poco。除非在数据库中遇到空值，否则代码可以正常工作。例如，如果数据库中的FirstName列包含空值，则抛出异常。
employee.FirstName = sqlreader.GetString(indexFirstName);
在这种情况下处理空值的最佳方法是什么?
我使用SQLdatareader从数据库构建poco。除非在数据库中遇到空值，否则代码可以正常工作。例如，如果数据库中的FirstName列包含空值，则抛出异常。
employee.FirstName = sqlreader.GetString(indexFirstName);
在这种情况下处理空值的最佳方法是什么?
我最近了解到iPhone应用程序能够接收几乎即时的通知。
这是以推送通知的形式提供的，这是一种定制的协议，可以保持与iPhone的数据连接，并向应用程序发送二进制数据包，它会以极快的速度弹出警报，从服务器应用程序发送到手机应用程序的响应时间为0.5 - 5秒。这是作为数据而不是SMS发送的，以非常非常小的数据包作为数据计划的一部分收费，而不是作为传入消息。
我想知道，如果，使用Android，有一个类似的设施，或者是否有可能实现接近这个使用Android api的东西。为了澄清，我将相似定义为:
不是短信，而是一些数据驱动的解决方案 尽可能的实时 是否可扩展，即作为移动应用程序的服务器部分，我可以在几秒钟内通知数千个应用程序实例
我欣赏的应用程序可以拉基于，HTTP请求/响应风格，但理想情况下，我不想轮询那么严重，只是为了检查通知;除此之外，它就像滴漏数据计划。
我在Visual Studio文本编辑器中有一个奇怪的错误。 所有空格都被"。"取代
public class Person
{
int age;
}
是这样的
public..class..Person..........................
{..................
..int age;...................
}.....................
我将设置重置为默认值。没有工作。 我也重新安装了VS2008。还是没用。 误差是多少?
我知道有很多关于如何在Java中获取日期的问题，但我想要一个使用新的Java 8日期API的例子。我也知道JodaTime库，但我想要一个不依赖于外部库的方法。
该函数需要符合以下限制:
从日期保存时间防止错误 输入是两个日期对象(没有时间，我知道LocalDateTime，但我需要用日期实例这样做)
在rails >4.0.0生成器使用before_action而不是before_filter创建CRUD操作。它似乎做着同样的事情。这两者有什么区别呢?
我创建了一个JS类来填充SG/Folder列表视图数据，当项目被修改时。(根据Jaime的方法) 当我操作在出版物中创建它们的项时，一切都很好。
例如:我打开一个组件或页面，自定义锁定列立即更新并显示我的用户名。
但是，当我转到子出版物并重复该过程时，我会看到一个窗口，询问我是想本地化还是编辑父项。如果我选择编辑父窗口，代码将无法工作。在最初的调试中，我还没有完全弄清楚。Chrome似乎吞下了这个错误，Firefox给了我一个神秘的答案:
时间戳:2012年6月22日下午3:42:54 错误:uncaught exception: [exception…]"组件返回失败代码:0x80004002 (NS_NOINTERFACE) [nsIWebProgress。DOMWindow]" nsresult: "0x80004002 (NS_NOINTERFACE)" 位置:"JS frame:: chrome://browser/content/tabbrowser.xml:::: line 545" 数据没有):
有人有什么初步想法吗?稍后我会试着发布一些代码……
来自PageEx.js的代码:
Type.registerNamespace("MyCompany.Tridion.RTFExtensions");
/*
* Constructor
*/
MyCompany.Tridion.RTFExtensions.PageEx = function (id) {
Type.enableInterface(this, "MyCompany.Tridion.RTFExtensions.PageEx");
this.addInterface("Tridion.ContentManager.Page", [id]);
var p = this.properties;
p.versionNumberString = undefined;
p.modifiedBy = undefined;
p.lockedBy = undefined;
p.approvalStatus = undefined;
p.publishDate = undefined;
p.previousVersion = undefined;
p.previousApprovalStatus = undefined;
p.customModifiedDate = undefined;
p.initialModifierUserName = undefined;
};
/*
* sends the list xml string for the item
*/
MyCompany.Tridion.RTFExtensions.PageEx.prototype.getListItemXmlAttributes = function (customAttributes) {
var attribs = {};
$extUtils.getListItemXmlAttributes(customAttributes,this, attribs);
return this.callBase("Tridion.ContentManager.Page", "getListItemXmlAttributes", [attribs]);
};
/*
* This method gets called when an item is opened from list view. node parameter has the information
* displayed in the list view as attributes. We are getting cutom data extender column information
* from this xml node and storing it in this class member for returning it from getListItemXmlAttributes method
*/
MyCompany.Tridion.RTFExtensions.PageEx.prototype.setDataFromList = function (node, parentId, timeStamp) {
$extUtils.setDataFromList(node,parentId,timeStamp,this);
this.callBase("Tridion.ContentManager.Page", "setDataFromList", [node, parentId, timeStamp]);
};
/*
* Gets item icon
*/
MyCompany.Tridion.RTFExtensions.PageEx.prototype.getItemIcon = function () {
var icon = this.callBase(this.defaultBase, "getItemIcon");
return icon;
};
utils.js中的代码:
// reloads the list view for the given id (used in list view data refresh when JS cant get the required data without reloading)
MyCompany.Tridion.RTFExtensions.Utilities.reloadListView = function (listTcmId) {
var registry = $models.getListsRegistry();
for(var key in registry)
{
var entry = $models.getItem(registry[key]);
if (entry && entry.getParentId() == listTcmId)
{
entry.unload();
return true;
}
}
return false;
}
/*
* This method gets called when an item is opened from list view. node parameter has the information
* displayed in the list view as attributes. We are getting cutom data extender column information
* from this xml node and storing it in this class member for returning it from getListItemXmlAttributes method
*/
MyCompany.Tridion.RTFExtensions.Utilities.setDataFromList = function (node, parentId, timeStamp, itemClicked) {
var p = itemClicked.properties;
if (!timeStamp || timeStamp > itemClicked.getTimeStamp()) {
var tmp;
if (tmp = node.getAttribute('Version')) {
p.versionNumberString = tmp;
p.previousVersion = tmp;
}
if (tmp = node.getAttribute('ModifiedBy')) {
p.modifiedBy = tmp;
p.initialModifierUserName = tmp;
}
if (tmp = node.getAttribute('LockedBy')) {
p.lockedBy = tmp;
}
if (tmp = node.getAttribute('ApprovalStatus')) {
p.approvalStatus = tmp;
p.previousApprovalStatus = tmp;
}
if (tmp = node.getAttribute('PublishDate')) {
p.publishDate = tmp;
}
if (p.customModifiedDate === undefined) {
if (tmp = node.getAttribute('Modified')) {
p.customModifiedDate = tmp;
}
}
}
}
/*
* sends the list xml string for the item in the list view.
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListItemXmlAttributes = function (customAttributes, listViewObject,attribs) {
var p = listViewObject.properties;
$extUtils.getListViewItemLockedByName(p,listViewObject);
if (customAttributes) {
for (var attr in customAttributes) {
attribs[attr] = customAttributes[attr];
}
}
attribs["Version"] = $extUtils.getListViewItemUpdatedVersion(p,listViewObject);
//modified name has to come after the version update...
$extUtils.getListViewItemModifiedByName(p,listViewObject);
attribs["ApprovalStatus"] = $extUtils.getListViewItemApprovalStatus(p,listViewObject);
attribs["PublishDate"] = $extUtils.getListViewItemPublishDate(p,listViewObject);
//set default values
if (p.versionNumberString != undefined) {
var iResult = p.versionNumberString.localeCompare(p.previousVersion);
if (p.previousVersion === undefined || iResult > 0) {
//it's been updated!
p.previousVersion = p.versionNumberString;
p.previousApprovalStatus = p.approvalStatus;
//also need to update modified date
p.customModifiedDate = $extUtils.getListViewItemUpdatedModifiedDate(p,listViewObject);
p.initialModifierUserName = p.modifiedBy;
}
}
attribs["Modified"] = p.customModifiedDate;
attribs["LockedBy"] = p.lockedBy;
attribs["ModifiedBy"] = p.modifiedBy;
};
/*
* This method sets the property of the Revisor owner on the item in the list view. however, if it's not the current user
* we have no way to look that up in JS so we have to reload the list view.
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemModifiedByName = function (p,listViewObject) {
var p = listViewObject.properties;
var xmlDoc = listViewObject.getXmlDocument();
if (xmlDoc) {
//modifier should always exist...
var modifierId = $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:VersionInfo/tcm:Revisor/@xlink:title");
if (modifierId != undefined) {
var u = Tridion.UI.UserSettings.getJsonUserSettings(true);
if (modifierId == u.User.Data.Name) {
var strDescription = u.User.Data.Description.split('(');
p.modifiedBy = strDescription[0];
return;
} else {
//we're in trouble...
//let's hope it's the initial modifier we had...
if (p.previousVersion == p.versionNumberString) {
//whew...
p.modifiedBy = p.initialModifierUserName;
return;
}
if (!$extUtils.reloadListView(listViewObject.getOrganizationalItemId())) {
//hrm. something failed on the reload? not sure what else to do:
p.modifiedBy = modifierId;
}
}
} else {
//shouldn't ever happen.
p.modifiedBy = "";
return;
}
}
};
/*
* This method sets the property of the lock owner on the item in the list view. however, if it's not the current user
* we have no way to look that up in JS so we have to reload the list view.
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemLockedByName = function (p,listViewObject) {
var xmlDoc = listViewObject.getXmlDocument();
if (xmlDoc) {
//this will be user id. no sense getting tcmid... can't look it up without async call
var lockedUserId = $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:VersionInfo/tcm:ItemLock/tcm:User/@xlink:title");
if (lockedUserId != undefined) {
//see if it's the current user. most likely...
var u = Tridion.UI.UserSettings.getJsonUserSettings(true);
if (lockedUserId == u.User.Data.Name) {
var strDescription = u.User.Data.Description.split('(');
p.lockedBy = strDescription[0];
return;
}
//it's not the current user. no synch way to do what we want, plus the JS call doesn't get the workflow version anyway. refresh the parent view
if (!$extUtils.reloadListView(listViewObject.getOrganizationalItemId())) {
//hrm. something failed on the reload? not sure what else to do:
p.lockedBy = lockedUserId;
}
} else {
//clear it out since there's no lock owner
p.lockedBy = "";
}
}
};
/*
* Gets the ApprovalStatus from the item
* This makes absolutely no sense... but for some reason the approval status gets wiped out when this method
* enters. so I had to use a "previous approval status" variable to maintain it. no idea why. I don't see anything
* else that should be touching it... but clearly something clears it out.
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemApprovalStatus = function (p,listViewObject) {
//check if the item has actually been modified.
if (p.versionNumberString != p.previousVersion) {
var xmlDoc = listViewObject.getXmlDocument();
if (xmlDoc) {
p.approvalStatus = $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:Data/tcm:ApprovalStatus/@xlink:title");
}
} else {
p.approvalStatus = p.previousApprovalStatus;
}
if (p.approvalStatus === undefined || p.approvalStatus.toUpperCase() == 'UNAPPROVED') {
var foo = p.approvalStatus;
p.approvalStatus = 'WIP';
}
return p.approvalStatus;
};
/*
* Gets the PublishDate from the item list view
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemPublishDate = function (p,listViewObject) {
//modification won't alter publish date.
var p = listViewObject.properties;
return p.publishDate;
};
/*
* get the modified date for the workflow version, overwrite OOB since that uses last major version
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemUpdatedModifiedDate = function (p,listViewObject) {
var xmlDoc = listViewObject.getXmlDocument();
var modDate = $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:VersionInfo/tcm:RevisionDate");
return modDate;
}
/*
* Gets the updated Version information from the item
*/
MyCompany.Tridion.RTFExtensions.Utilities.getListViewItemUpdatedVersion = function (p,listViewObject) {
var p = listViewObject.properties;
var xmlDoc = listViewObject.getXmlDocument();
var newVersionString = undefined;
if (xmlDoc) {
newVersionString = String.format("{0}.{1}", $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:VersionInfo/tcm:Version"), $xml.getInnerText(xmlDoc, "/tcm:*/tcm:Info/tcm:VersionInfo/tcm:Revision"));
}
if (newVersionString != undefined) {
//want to ensure we're getting a LATER version than we had (because it will try to load the non-workflow version afterwards...
var iResult = newVersionString.localeCompare(p.previousVersion);
if (p.previousVersion === undefined || iResult > 0) {
p.versionNumberString = newVersionString;
} else {
p.versionNumberString = p.previousVersion;
}
} else {
p.versionNumberString = p.previousVersion;
}
return p.versionNumberString;
};
function launchPopup(winURL, winName, winFeatures, winObj) {
// this will hold our opened window
var theWin;
// first check to see if the window already exists
if (winObj != null) {
// the window has already been created, but did the user close it?
// if so, then reopen it. Otherwise make it the active window.
if (!winObj.closed) {
winObj.focus();
return winObj;
}
// otherwise fall through to the code below to re-open the window
}
// if we get here, then the window hasn't been created yet, or it
// was closed by the user.
theWin = window.open(winURL, winName, winFeatures);
return theWin;
}
var $extUtils = MyCompany.Tridion.RTFExtensions.Utilities;
在这个问题中Erik需要在Node.js中生成一个安全的随机令牌。这是crypto方法。生成一个随机Buffer的randomBytes。但是，节点中的base64编码不是url安全的，它包含/和+而不是-和_。因此，我发现生成这种令牌的最简单方法是
require('crypto').randomBytes(48, function(ex, buf) {
token = buf.toString('base64').replace(/\//g,'_').replace(/\+/g,'-');
});
还有更优雅的方式吗?
我注意到下面的代码在Python中是合法的。我的问题是为什么?有什么特别的原因吗?
n = 5
while n != 0:
print n
n -= 1
else:
print "what the..."
许多初学者在尝试在while或for循环中放入if/else块时无意中发现了这种语法，并且没有正确地缩进else。解决方案是确保else块与if块对齐，假设您打算对它们进行配对。这个问题解释了为什么它没有导致语法错误，以及产生的代码意味着什么。我还得到了一个IndentationError。我该怎么解决呢?，用于报告语法错误的情况。
如何将std::vector的内容打印到屏幕上?
实现以下操作符<<的解决方案也很好:
template<container C, class T, String delim = ", ", String open = "[", String close = "]">
std::ostream & operator<<(std::ostream & o, const C<T> & x)
{
// ... What can I write here?
}
以下是目前为止我所做的，没有单独的函数:
#include <iostream>
#include <fstream>
#include <string>
#include <cmath>
#include <vector>
#include <sstream>
#include <cstdio>
using namespace std;
int main()
{
ifstream file("maze.txt");
if (file) {
vector<char> vec(istreambuf_iterator<char>(file), (istreambuf_iterator<char>()));
vector<char> path;
int x = 17;
char entrance = vec.at(16);
char firstsquare = vec.at(x);
if (entrance == 'S') {
path.push_back(entrance);
}
for (x = 17; isalpha(firstsquare); x++) {
path.push_back(firstsquare);
}
for (int i = 0; i < path.size(); i++) {
cout << path[i] << " ";
}
cout << endl;
return 0;
}
}
我经常听到有人说c++是一种上下文敏感的语言。举个例子:
a b(c);
这是变量定义还是函数声明?这取决于符号c的含义。如果c是一个变量，则ab (c);定义一个名为b的类型为a的变量。它直接用c初始化。但如果c是类型，则ab (c);声明一个名为b的函数，该函数接受c并返回a。
如果您查找上下文无关语言的定义，它基本上会告诉您，所有语法规则的左侧必须恰好包含一个非终结符。另一方面，上下文敏感语法允许在左侧使用任意的终结符和非终结符字符串。
浏览“c++程序设计语言”的附录A，我找不到一条语法规则，它的左边除了一个非终结符之外，还有其他任何东西。这意味着c++是上下文无关的。(当然，每一种与上下文无关的语言也是与上下文相关的，因为与上下文无关的语言构成了与上下文相关的语言的一个子集，但这不是重点。)
那么，c++是上下文无关的还是上下文敏感的?