Instantiation is the process of creating objects from a class in most object oriented and object based languages. In the C++ language, instantiation is the process of creating a class or function from a class template or function template.
Questions tagged [instantiation]
2609 questions
90
votes
4 answers
How to instantiate class from name string in Rails?
How we can instantiate class from it's name string in Ruby-on-Rails?
For example we have it's name in database in format like "ClassName" or "my_super_class_name".
How we can create object from it?
Solution:
Was looking for it myself, but not found,…
Vjatseslav Gedrovits
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89
votes
11 answers
Declaring an object before initializing it in c++
Is it possible to declare a variable in c++ without instantiating it? I want to do something like this:
Animal a;
if( happyDay() )
a( "puppies" ); //constructor call
else
a( "toads" );
Basially, I just want to declare a outside of the…
Quantum7
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87
votes
7 answers
How is an instance initializer different from a constructor?
In other words, why would you need an instance initializer? What difference or advantage do you have in writing a instance initializer over a constructor?
Ajay
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84
votes
9 answers
How to create inline objects with properties?
In Javascript it would be:
var newObject = { 'propertyName' : 'propertyValue' };
newObject.propertyName; // returns "propertyValue"
But the same syntax in Python would create a dictionary, and that's not what I want
new_object = {'propertyName':…
Jader Dias
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83
votes
6 answers
Is there a way to instantiate a class without calling __init__?
Is there a way to circumvent the constructor __init__ of a class in python?
Example:
class A(object):
def __init__(self):
print "FAILURE"
def Print(self):
print "YEHAA"
Now I would like to create an instance of A. It…
Woltan
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76
votes
8 answers
What's the difference between dict() and {}?
So let's say I wanna make a dictionary. We'll call it d. But there are multiple ways to initialize a dictionary in Python! For example, I could do this:
d = {'hash': 'bang', 'slash': 'dot'}
Or I could do this:
d = dict(hash='bang', slash='dot')
Or…
verix
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76
votes
2 answers
PHP class instantiation. To use or not to use the parentheses?
I've always assumed that - in the absence of constructor parameters - the parentheses (curly brackets) follow the class name when creating a class instance, were optional, and that you could include or exclude them at your own personal whim.
That…
Atli
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62
votes
7 answers
Does { } act like ( ) when creating a new object in C#?
I just noticed that using {} instead of () gives the same results when constructing an object.
class Customer
{
public string name;
public string ID {get; set;}
}
static void Main()
{
Customer c1= new Customer{}; //Is this a…
user4451265
60
votes
6 answers
Why do I get an error instantiating an interface?
I have a class and an interface, and when I try to instantiate the interface, I get an error:
Cannot create an instance of the abstract class or interface
My code is below:
namespace MyNamespace
{
public interface IUser
{
int…
Alex
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60
votes
6 answers
How do I force a particular instance of a C++ template to instantiate?
See title. I have a template. I want to force a particular instance of a template to instantiate. How do I do this?
More specifically, can you force an abstract template class to instantiate?
I might elaborate as I have the same question. In my…
anon
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48
votes
7 answers
How does one instantiate an array of maps in Java?
I can declare an array of maps using generics to specify the map type:
private Map[] myMaps;
However, I can't figure out how to instantiate it properly:
myMaps = new HashMap[count]; // gives "generic array…
Karl von L
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47
votes
4 answers
In PHP 5 can I instantiate a class dynamically?
Is it possible to dynamically instantiate a class using a variable? For example is something like this possible in PHP?
class foo
{
public $something;
}
$class_name = "foo";
$f = new $class_name();
Bijou Trouvaille
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46
votes
2 answers
Can't Instantiate Map...well why not?
Map>> k = new Map>>();
This line is in my code. I'd like to instantiate a Map that contains a String then an ArrayList of Pairs of Strings and Integers.
Pair is a…
PinkElephantsOnParade
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45
votes
3 answers
Instantiate a class from its textual name
Don't ask me why but I need to do the following:
string ClassName = "SomeClassName";
object o = MagicallyCreateInstance("SomeClassName");
I want to know how many ways there are to do this is and which approach to use in which…
Raheel Khan
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44
votes
5 answers
Determine if a type is static
Let's say I have a Type called type.
I want to determine if I can do this with my type (without actually doing this to each type):
If type is System.Windows.Point then I could do this:
Point point1 = new Point();
However if type is…
Beaker
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