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Pure virtual function with implementation
...he base type can still define an implementation. A derived class can explicitly call the base class implementation (if access permissions allow it) by using a fully-scoped name (by calling A::f() in your example - if A::f() were public or protected). Something like:
class B : public A {
virtu...
How to use a variable to specify column name in ggplot
...
If for whatever reason you'd rather not use aes_string, you could change it to (the somewhat more cumbersome):
ggplot( rates.by.groups, aes(x=name, y=rate, colour= get(column),
group=get(column) ) )
...
How to list the files inside a JAR file?
...e == null)
break;
String name = e.getName();
if (name.startsWith("path/to/your/dir/")) {
/* Do something with this entry. */
...
}
}
}
else {
/* Fail... */
}
Note that in Java 7, you can create a FileSystem from the JAR (zip) file, and then use NIO's directory wa...
“android.view.WindowManager$BadTokenException: Unable to add window” on buider.show()
From my main activity , I need to call an inner class and in a method within the class, I need to show AlertDialog . After dismissing it, when the OK button is pressed, forward to Google Play for purchase.
...
Are there any SHA-256 javascript implementations that are generally considered trustworthy?
I am writing a login for a forum, and need to hash the password client side in javascript before sending it on to the server. I'm having trouble figuring out which SHA-256 implementation I can actually trust. I was expecting there to be some kind of authoritative script that everyone used, but I'm f...
What is a covariant return type?
... to be a subtype of the overridden method's return type.
To clarify this with an example, a common case is Object.clone() - which is declared to return a type of Object. You could override this in your own class as follows:
public class MyFoo
{
...
// Note covariant return here, method do...
Is embedding background image data into CSS as Base64 good or bad practice?
...
It's not a good idea when you want your images and style information to be cached separately. Also if you encode a large image or a significant number of images in to your css file it will take the browser longer to download...
How do I detect that an iOS app is running on a jailbroken phone?
...
It depends what you mean by jailbreak. In the simple case, you should be able to see if Cydia is installed and go by that - something like
NSString *filePath = @"/Applications/Cydia.app";
if ([[NSFileManager defaultManager]...
'UserControl' constructor with parameters in C#
Call me crazy, but I'm the type of guy that likes constructors with parameters (if needed), as opposed to a constructor with no parameters followed by setting properties. My thought process: if the properties are required to actually construct the object, they should go in the constructor. I get two...
How do I use method overloading in Python?
...
It's method overloading not method overriding. And in Python, you do it all in one function:
class A:
def stackoverflow(self, i='some_default_value'):
print 'only method'
ob=A()
ob.stackoverflow(2)
ob.stack...