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Using reference variable passed to the constructor in other functions c#


Using reference variable passed to the constructor in other functions c#

By : user2951429
Date : November 18 2020, 11:13 AM
Does that help I don't think that passing the collection as ref is what you really nead. This approach is probably what you're looking for because I guess you want to modify the collection and not to replace it because it would break your databinding if any (and I'm pretty sure you have it databound):
1st control: in the 1st control pass the collection to a property that you add to the 2nd control:
code :
private void Menu_Click(object sender, RoutedEventArgs e)
{
    Window window = new Window
    {
        Title = "UserControl2",
        Content = new ColumnDataControl() 
        {
            CollectionOfData = collectionOfData
        };
    };
    window.ShowDialog();

}
public ColumnDataControl() { }

ObservableCollection<data> CollectionOfData { get; set; }

private button_click(object sender, RoutedEventArgs e)
{
    CollectionOfData.Add(...);
}


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Are there any performance gains when creating new variable passed by reference vs. passed by value?

Are there any performance gains when creating new variable passed by reference vs. passed by value?


By : user3126668
Date : March 29 2020, 07:55 AM
I wish this helpful for you If all you are interested in is performance, then as a general rule, pass by reference performs better than pass by value.
object reference passed through constructor

object reference passed through constructor


By : KenG
Date : March 29 2020, 07:55 AM
hope this fix your issue As mentioned - this may be a sign your class is doing too much, however, there is a commonly used 'solution' to this problem.
The builder pattern is often used in this situation, but it's also very useful when you have many constructors with different arguments, the builder is good because it makes the meaning of the arguments clearer, particularly when boolean literals are used.
code :
AreodynamicCalculator calc = AreodynamicCalculator.builder()
    .config(theAircraftConfiguration)
    .addAileron(aileronOne)
    .addAileron(aileronTwo)
    .addElevator(elevatorOne)
    .addElevator(elevatorTwo)
    .addRudder(rudderOne)
    .addRudder(rudderTwo)
    .build()
class AreodynamicCalculator {
    public static class Builder {
        AircraftConfiguration config;
        Aileron aileronOne;
        Aileron aileronTwo;
        Elevator elevatorOne;
        Elevator elevatorTwo;
        ...

        public Builder config(AircraftConfiguration config) {
            this.config = config;
            return this;
        }

        public Builder addAileron(Aileron aileron) {
            if (this.aileronOne == null) {
                this.aileronOne = aileron;
            } else {
                this.aileronTwo = aileron;
            }
            return this;
        }

        // adders / setters for other fields.

        public AreodynamicCalculator build() {
            return new AreodynamicCalculator(config, aileronOne, aileronTwo ... );
        }
    }

    // this is the AircraftConfiguration constructor, it's now private because
    // the way to create AircraftConfiguration objects is via the builder
    //
    private AircraftConfiguration config, AileronOne aOne, AileronTwo aTwo, ElevatorOne eOne, ElevatorTwo eTwo, Rudder r, Rudder rr, RateGyros rG) {
        /// assign fields
    }
}
Within C++ functions, how are Rcpp objects passed to other functions (by reference or by copy)?

Within C++ functions, how are Rcpp objects passed to other functions (by reference or by copy)?


By : Ushio Okasaki Brian
Date : March 29 2020, 07:55 AM
wish of those help There is no deep copy in Rcpp unless you ask for it with clone. When you pass by value, you are making a new List object but it uses the same underlying R object.
So the different is small between pass by value and pass by reference.
code :
#include <Rcpp.h>
using namespace Rcpp  ;

#define DBG(MSG,X) Rprintf("%20s SEXP=<%p>. List=%p\n", MSG, (SEXP)X, &X ) ;

void fun_copy( List x, const char* idx ){
    x[idx] = "foo" ;
    DBG( "in fun_copy: ", x) ;

}
void fun_ref( List& x, const char* idx ){
    x[idx] = "bar" ;
    DBG( "in fun_ref: ", x) ;
}


// [[Rcpp::export]]
void test_copy(){

    // create a list of 3 components
    List data = List::create( _["a"] = 1, _["b"] = 2 ) ;
    DBG( "initial: ", data) ;

    fun_copy( data, "a") ;
    DBG( "\nafter fun_copy (1): ", data) ;

    // alter the 1st component of ths list, passed by value
    fun_copy( data, "d") ;
    DBG( "\nafter fun_copy (2): ", data) ;


}

// [[Rcpp::export]]
void test_ref(){

    // create a list of 3 components
    List data = List::create( _["a"] = 1, _["b"] = 2 ) ;
    DBG( "initial: ", data) ;

    fun_ref( data, "a") ;
    DBG( "\nafter fun_ref (1): ", data) ;

    // alter the 1st component of ths list, passed by value
    fun_ref( data, "d") ;
    DBG( "\nafter fun_ref (2): ", data) ;


}
> test_copy()
           initial:  SEXP=<0x7ff97c26c278>. List=0x7fff5b909fd0
       in fun_copy:  SEXP=<0x7ff97c26c278>. List=0x7fff5b909f30

after fun_copy (1):  SEXP=<0x7ff97c26c278>. List=0x7fff5b909fd0
$a
[1] "foo"

$b
[1] 2

       in fun_copy:  SEXP=<0x7ff97b2b3ed8>. List=0x7fff5b909f20

after fun_copy (2):  SEXP=<0x7ff97c26c278>. List=0x7fff5b909fd0
$a
[1] "foo"

$b
[1] 2
           initial:  SEXP=<0x7fda4926d278>. List=0x7fff5bb5efd0
       in fun_copy:  SEXP=<0x7fda4926d278>. List=0x7fff5bb5ef30
after fun_copy (1):  SEXP=<0x7fda4926d278>. List=0x7fff5bb5efd0
       in fun_copy:  SEXP=<0x7fda48989120>. List=0x7fff5bb5ef20
after fun_copy (2):  SEXP=<0x7fda4926d278>. List=0x7fff5bb5efd0
> test_ref()
           initial:  SEXP=<0x7ff97c0e0f80>. List=0x7fff5b909fd0
        in fun_ref:  SEXP=<0x7ff97c0e0f80>. List=0x7fff5b909fd0

  after fun_ref(1):  SEXP=<0x7ff97c0e0f80>. List=0x7fff5b909fd0
$a
[1] "bar"

$b
[1] 2

        in fun_ref:  SEXP=<0x7ff97b5254c8>. List=0x7fff5b909fd0

  after fun_ref(2):  SEXP=<0x7ff97b5254c8>. List=0x7fff5b909fd0
$a
[1] "bar"

$b
[1] 2

$d
[1] "bar"
Are arguments passed via `&&` useful for non constructor functions?

Are arguments passed via `&&` useful for non constructor functions?


By : user3661397
Date : March 29 2020, 07:55 AM
should help you out Optimizing for r-values
Comparing void setData(std::string arg) and void setData(std::string&& arg). In the first case I assume setData moves the data into place
code :
class Widget {
  std::string data;
 public:
  void setData(std::string data) { this->data = std::move(data); }
};
w.setData(std::move(data));
class Widget {
  std::string data;
 public:
  void setData(std::string&& data) { this->data = std::move(data); }
};
Class Member Not a Reference but Constructor with Argument Passed by Reference

Class Member Not a Reference but Constructor with Argument Passed by Reference


By : AlperKaanYıldırım
Date : March 29 2020, 07:55 AM
I wish did fix the issue. What happens when you have something like this in C++: , That's just the same as the following code:
code :
void foo(obj& b) {
    obj a(b);
}
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