Questions tagged [reflection]
Reflection is the ability of a program to observe and/or modify its structure and/or behavior at runtime. Reflection is dependent on the supporting programming language - please tag the programming language being used when using this tag.
reflection
25,228
questions
2551
votes
24
answers
1.0m
views
What is reflection and why is it useful?
What is reflection, and why is it useful?
I'm particularly interested in Java, but I assume the principles are the same in any language.
- 48.2k
2446
votes
18
answers
1.2m
views
Calling a function of a module by using its name (a string)
How do I call a function, using a string with the function's name? For example:
import foo
func_name = "bar"
call(foo, func_name) # calls foo.bar()
- 36.3k
1300
votes
9
answers
365k
views
How do I call a generic method using a Type variable?
What's the best way to call a generic method when the type parameter isn't known at compile time, but instead is obtained dynamically at runtime?
Consider the following sample code - inside the ...
- 44.1k
1244
votes
32
answers
1.0m
views
How can I create a generic array in Java?
Due to the implementation of Java generics, you can't have code like this:
public class GenSet<E> {
private E a[];
public GenSet() {
a = new E[INITIAL_ARRAY_LENGTH]; // Error: ...
- 25.5k
1196
votes
25
answers
1.1m
views
Get property value from string using reflection
I am trying implement the Data transformation using Reflection1 example in my code.
The GetSourceValue function has a switch comparing various types, but I want to remove these types and properties ...
- 16.7k
945
votes
31
answers
808k
views
How do I get the path of the assembly the code is in?
Is there a way to get the path for the assembly in which the current code resides? I do not want the path of the calling assembly, just the one containing the code.
Basically my unit test needs to ...
- 121k
932
votes
11
answers
753k
views
How to create a new object instance from a Type
One may not always know the Type of an object at compile-time, but may need to create an instance of the Type.
How do you get a new object instance from a Type?
- 83.7k
784
votes
11
answers
772k
views
How to get the list of properties of a class?
How do I get a list of all the properties of a class?
Sukesh
778
votes
23
answers
1.1m
views
How do I invoke a Java method when given the method name as a string?
If I have two variables:
Object obj;
String methodName = "getName";
Without knowing the class of obj, how can I call the method identified by methodName on it?
The method being called has no ...
- 77.9k
723
votes
16
answers
345k
views
How to determine if a type implements an interface with C# reflection
Does reflection in C# offer a way to determine if some given System.Type type models some interface?
public interface IMyInterface {}
public class MyType : IMyInterface {}
// should yield 'true'
...
- 22.5k
686
votes
11
answers
621k
views
C# getting its own class name
If I have a class called MyProgram, is there a way of retrieving "MyProgram" as a string?
- 43.5k
671
votes
30
answers
869k
views
Get generic type of class at runtime
How can I achieve this?
public class GenericClass<T>
{
public Type getMyType()
{
//How do I return the type of T?
}
}
Everything I have tried so far always returns type ...
- 6,735
666
votes
19
answers
399k
views
Getting all types that implement an interface
Using reflection, how can I get all types that implement an interface with C# 3.0/.NET 3.5 with the least code, and minimizing iterations?
This is what I want to re-write:
foreach (Type t in this....
- 81.3k
652
votes
30
answers
528k
views
Can you find all classes in a package using reflection?
Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. Package, it would seem like no.)
- 81.2k
611
votes
15
answers
359k
views
Checking if a variable is defined?
How can I check whether a variable is defined in Ruby? Is there an isset-type method available?
- 351k
607
votes
4
answers
179k
views
What are the use(s) for struct tags in Go?
In the Go Language Specification, it mentions a brief overview of tags:
A field declaration may be followed by an optional string literal tag,
which becomes an attribute for all the fields in ...
- 14.3k
601
votes
16
answers
184k
views
Programmatic equivalent of default(Type)
I'm using reflection to loop through a Type's properties and set certain types to their default. Now, I could do a switch on the type and set the default(Type) explicitly, but I'd rather do it in one ...
- 83.7k
594
votes
21
answers
1.1m
views
How to list all functions in a module?
I have a Python module installed on my system and I'd like to be able to see what functions/classes/methods are available in it.
I want to call the help function on each one. In Ruby I can do ...
- 7,754
584
votes
27
answers
430k
views
Getting attributes of Enum's value
I would like to know if it is possible to get attributes of the enum values and not of the enum itself? For example, suppose I have the following enum:
using System.ComponentModel; // for ...
- 11.1k
579
votes
26
answers
623k
views
How do I get the path and name of the python file that is currently executing?
I have scripts calling other script files but I need to get the filepath of the file that is currently running within the process.
For example, let's say I have three files. Using execfile:
...
- 190k
577
votes
17
answers
380k
views
Change private static final field using Java reflection
I have a class with a private static final field that, unfortunately, I need to change it at run-time.
Using reflection I get this error: java.lang.IllegalAccessException: Can not set static final ...
- 6,673
562
votes
14
answers
379k
views
How to read the value of a private field from a different class in Java?
I have a poorly designed class in a 3rd-party JAR and I need to access one of its private fields. For example,
why should I need to choose private field is it necessary?
class IWasDesignedPoorly {
...
- 70.5k
545
votes
23
answers
487k
views
Getting the name of the currently executing method
Is there a way to get the name of the currently executing method in Java?
- 55.3k
509
votes
16
answers
284k
views
What is the difference between instanceof and Class.isAssignableFrom(...)?
Which of the following is better?
a instanceof B
or
B.class.isAssignableFrom(a.getClass())
The only difference that I know of is, when 'a' is null, the first returns false, while the second throws ...
- 6,307
440
votes
32
answers
325k
views
Get class name of object as string in Swift
Getting the classname of an object as String using:
object_getClassName(myViewController)
returns something like this:
_TtC5AppName22CalendarViewController
I am looking for the pure version: "...
- 11.4k
437
votes
15
answers
299k
views
Test if object implements interface
What is the simplest way of testing if an object implements a given interface in C#? (Answer to this question
in Java)
- 10.2k
421
votes
13
answers
322k
views
How can I get a list of all classes within current module in Python?
I've seen plenty of examples of people extracting all of the classes from a module, usually something like:
# foo.py
class Foo:
pass
# test.py
import inspect
import foo
for name, obj in inspect....
- 7,841
419
votes
10
answers
124k
views
Open Source Alternatives to Reflector? [closed]
Just to ask if anyone knows of an open source alternative to RedGate's Reflector? I'm interested in checking out how a tool similar to Reflector actually works.
Note, if you know of a free but not ...
- 44.3k
417
votes
16
answers
60k
views
Is a Java string really immutable?
We all know that String is immutable in Java, but check the following code:
String s1 = "Hello World";
String s2 = "Hello World";
String s3 = s1.substring(6);
System.out.println(s1); // Hello ...
- 3,266
416
votes
5
answers
260k
views
How do I check if a type is a subtype OR the type of an object?
To check if a type is a subclass of another type in C#, it's easy:
typeof (SubClass).IsSubclassOf(typeof (BaseClass)); // returns true
However, this will fail:
typeof (BaseClass).IsSubclassOf(...
- 38k
394
votes
11
answers
401k
views
Casting a variable using a Type variable
In C# can I cast a variable of type object to a variable of type T where T is defined in a Type variable?
- 12.2k
385
votes
10
answers
343k
views
Set object property using reflection
Is there a way in C# where I can use reflection to set an object property?
Ex:
MyObject obj = new MyObject();
obj.Name = "Value";
I want to set obj.Name with reflection. Something like:
Reflection....
- 10.5k
385
votes
12
answers
229k
views
How do I use reflection to invoke a private method?
There are a group of private methods in my class, and I need to call one dynamically based on an input value. Both the invoking code and the target methods are in the same instance. The code looks ...
- 11.7k
381
votes
10
answers
583k
views
Creating an instance using the class name and calling constructor
Is there a way to create an instance of a particular class given the class name (dynamic) and pass parameters to its constructor.
Something like:
Object object = createInstance("mypackage.MyClass","...
- 4,107
380
votes
16
answers
1.4m
views
What could cause java.lang.reflect.InvocationTargetException?
Well, I've tried to understand and read what could cause it but I just can't get it:
I have this somewhere in my code:
try{
..
m.invoke(testObject);
..
} catch(AssertionError e){
...
} catch(...
- 4,719
372
votes
16
answers
71k
views
Why does C++ not have reflection?
This is a somewhat bizarre question. My objectives are to understand the language design decision and to identify the possibilities of reflection in C++.
Why C++ language committee did not go towards ...
- 20.8k
369
votes
12
answers
354k
views
Setting a property by reflection with a string value
I'd like to set a property of an object through Reflection, with a value of type string.
So, for instance, suppose I have a Ship class, with a property of Latitude, which is a double.
Here's what I'd ...
- 10.3k
357
votes
16
answers
192k
views
Check if a class is derived from a generic class
I have a generic class in my project with derived classes.
public class GenericClass<T> : GenericInterface<T>
{
}
public class Test : GenericClass<SomeType>
{
}
Is there any way ...
- 11.8k
355
votes
7
answers
96k
views
Convert.ChangeType() fails on Nullable Types
I want to convert a string to an object property value, whose name I have as a string. I am trying to do this like so:
string modelProperty = "Some Property Name";
string value = "SomeValue";
var ...
- 3,869
353
votes
24
answers
220k
views
How to tell if a JavaScript function is defined
How do you tell if a function in JavaScript is defined?
I want to do something like this
function something_cool(text, callback) {
alert(text);
if( callback != null ) callback();
}
But it ...
- 5,407
350
votes
36
answers
278k
views
How to get function parameter names/values dynamically?
Is there a way to get the function parameter names of a function dynamically?
Let’s say my function looks like this:
function doSomething(param1, param2, .... paramN){
// fill an array with the ...
- 5,711
346
votes
16
answers
467k
views
Reflection - get attribute name and value on property
I have a class, lets call it Book with a property called Name. With that property, I have an attribute associated with it.
public class Book
{
[Author("AuthorName")]
public string Name
{
...
user619891
332
votes
28
answers
292k
views
How can I add reflection to a C++ application?
I'd like to be able to introspect a C++ class for its name, contents (i.e. members and their types) etc. I'm talking native C++ here, not managed C++, which has reflection. I realise C++ supplies some ...
- 27.9k
317
votes
11
answers
214k
views
Getting all types in a namespace via reflection
How do you get all the classes in a namespace through reflection in C#?
Chethan
280
votes
18
answers
238k
views
Type.GetType("namespace.a.b.ClassName") returns null
This code:
Type.GetType("namespace.a.b.ClassName")
returns null.
I have in the usings:
using namespace.a.b;
The type exists, it's in a different class library, and I need to get it by it's ...
- 70.8k
280
votes
11
answers
229k
views
Find a private field with Reflection?
Given this class
class Foo
{
// Want to find _bar with reflection
[SomeAttribute]
private string _bar;
public string BigBar
{
get { return this._bar; }
}
}
I want to ...
- 72.9k
279
votes
14
answers
119k
views
How to determine if a type implements a specific generic interface type
Assume the following type definitions:
public interface IFoo<T> : IBar<T> {}
public class Foo<T> : IFoo<T> {}
How do I find out whether the type Foo implements the generic ...
- 14.6k
272
votes
13
answers
344k
views
Get name of property as a string
(See below solution I created using the answer I accepted)
I'm trying to improve the maintainability of some code involving reflection. The app has a .NET Remoting interface exposing (among other ...
- 4,626
264
votes
3
answers
56k
views
BindingFlags.IgnoreCase not working for Type.GetProperty()?
Imagine the following
A type T has a field Company.
When executing the following method it works perfectly:
Type t = typeof(T);
t.GetProperty("Company")
Whith the following call I get null though
...
- 92.6k
264
votes
12
answers
387k
views
Tool to generate JSON schema from JSON data [closed]
We have this json schema draft. I would like to get a sample of my JSON data and generate a skeleton for the JSON schema, that I can rework manually, adding things like description, required, etc, ...
- 43.3k