default-value

问题 Since PHP 5.3, it is possible to leave out the middle part of the ternary operator. Expression expr1 ?: expr3 returns expr1 if expr1 evaluates to TRUE, and expr3 otherwise. Is there any better or more concise way than following code to set default value of variables? $v = isset($v) ? $v : "default value"; 回答1: Here is a shorter syntax: isset($v) || $v="default value"; 回答2: TL;DR - No, that expression can't be made any shorter. What you want is for the shortened ternary expression to perform

问题 I have this code: if(isset($_POST['search'])) { $res1=mysql_query("SELECT * FROM aircraft where acode = '$_POST[ac]'") or die(mysql_error()); while($row=mysql_fetch_array($res1)) { $airc=$row['acode']; $amode=$row['amodel']; $stat=$row['status']; $rem=$row['remarks']; echo "<center><table><form name=\"frmMain\" method=\"post\"> <tr><td><font face=consolas><b>Aircraft Code:</b></font></td><td><input type=text name=arc value='$airc' readonly=readonly></td></tr> <tr><td><font face=consolas><b

问题 I have a simple script in jQuery that works perfectly with jQuery 1.5.2 as you can see in this jsFiddle. What is supposed to happen is that when you bring focus to the text field, the default value is removed. And when if you leave the field blank, the original default value is put back in place. http://jsfiddle.net/kHBsD/ However, the same exact code, where only jQuery 1.6.3 is used instead, is not working. (Not working means that the default value remains in the text box until you manually

问题 How to set default value for a field to other column in Mysql I have done it oracle with virtual field but I do not know how to do it in Mysql this is my table: create table TSM_TRANSACTION_TBL ( TRANS_ID INT primary key auto_increment, LOCATION_ID INT, TRANS_DATE DATE, RESOURCE_ID INT, TS_ID INT, MAX_VALUE INT, BOOKED_UNITS INT default 0, REMAINING INT default MAX_VALUE - BOOKED_UNITS, BOOKED INT not null, USER_ID INT, TRANS_TIME TIMESTAMP ) 回答1: As documented under Data Type Default Values:

问题 The question is simple: #include <iostream> enum SomeEnum { EValue1 = 1, EValue2 = 4 }; int main() { SomeEnum enummy; std::cout << (int)enummy; } What will be the output? Note: This is not an interview, this is code inherited by me from previous developers. Streaming operator here is just for example, actual inherited code doesn't have it. 回答1: The program has Undefined Behavior. The value of enummy is indeterminate. Conceptually there is no difference between your code and the following code

问题 When you define a function in Python with an array parameter, what is the scope of that parameter? This example is taken from the Python tutorial: def f(a, L=[]): L.append(a) return L print f(1) print f(2) print f(3) Prints: [1] [1, 2] [1, 2, 3] I'm not quite sure if I understand what's happening here. Does this mean that the scope of the array is outside of the function? Why does the array remember its values from call to call? Coming from other languages, I would expect this behavior only

问题 Is there any difference on whether I initialize an integer variable like: int i = 0; int i; Does the compiler or CLR treat this as the same thing? IIRC, I think they're both treated as the same thing, but I can't seem to find the article. 回答1: I looked at the IL (using ildasm) and its true that only the int set to 0 is really set to 0 in the constructor. public class Class1 { int setToZero = 0; int notSet; } Generates: .method public hidebysig specialname rtspecialname instance void .ctor()

问题 I've run into another problem using C# 4.0 with optional parameters. How do I invoke a function (or rather a constructor, I have the ConstructorInfo object) for which I know it doesn't require any parameters? Here is the code I use now: type.GetParameterlessConstructor() .Invoke(BindingFlags.OptionalParamBinding | BindingFlags.InvokeMethod | BindingFlags.CreateInstance, null, new object[0], CultureInfo.InvariantCulture); (I've just tried with different BindingFlags ).

问题 I would like to have a optional argument that will default to a value if only the flag is present with no value specified, but store a user-specified value instead of the default if the user specifies a value. Is there already an action available for this? An example: python script.py --example # args.example would equal a default value of 1 python script.py --example 2 # args.example would equal a default value of 2 I can create an action, but wanted to see if there was an existing way to do

问题 I would like to know how to set the default value of a form Combobox field as the value in the database in Symfony2. The explanation is as below: This is the code of the entity I am dealing with: <?php namespace Ikproj\HomeBundle\Entity; use Doctrine\ORM\Mapping as ORM; /** * User * * @ORM\Table(name="user") * @ORM\Entity(repositoryClass="Ikproj\HomeBundle\Entity\UserRepository") */ class User { /** * @var integer * * @ORM\Column(name="id_user", type="integer") * @ORM\Id * @ORM\GeneratedValue