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Is it possible to assign a new object into 'this'?


Is it possible to assign a new object into 'this'?

By : Luca Blackskettle
Date : October 16 2020, 06:10 PM
I hope this helps you . You cannot assign a new object to this. This always references the current object.
Why don't you just set X and invoke the Calculting() method from Set_X? This will change the current object's state.
code :


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How to assign properties generically using Expression.Assign selector with target type of object?

How to assign properties generically using Expression.Assign selector with target type of object?


By : Jaylodet
Date : March 29 2020, 07:55 AM
hope this fix your issue I am trying to use an Expression selector to generically assign properties from one type of object to another where the properties are of various types. This is the code I have so far: , OK, I got this working with the following code:
code :
var type1 = new Type1();
var type2 = new Type2();

...

var propMap = new List<Tuple<Expression<Func<Type1, object>>, Expression<Func<TradeStaticAttributesItemModel, object>>>>
    {
        new Tuple<Expression<Func<Type1, object>>, Expression<Func<Type2, object>>>(x => x.Prop1, x => x.Prop1),
        new Tuple<Expression<Func<Type1, object>>, Expression<Func<Type2, object>>>(x => x.Prop2, x => x.Prop2)
    };

foreach (var prop in propMap)
{
    if (prop.Item1.Compile()(type1) != prop.Item2.Compile()(type2))
    {
        ParameterExpression valueParameterExpression = Expression.Parameter(typeof(object));

        // This handles nullable types
        Expression targetExpression = prop.Item1.Body is UnaryExpression ? ((UnaryExpression)prop.Item1.Body).Operand : prop.Item1.Body;

        var assign = Expression.Lambda<Action<Type1, object>>(
            Expression.Assign(targetExpression, Expression.Convert(valueParameterExpression, targetExpression.Type)),
            prop.Item1.Parameters.Single(),
            valueParameterExpression);

        Action<Type1, object> setter = assign.Compile();
        setter(type1, prop.Item2.Compile()(type2));
    }
}
To copy from one object to another, can I assign the variables directly, or must I assign their properties individually?

To copy from one object to another, can I assign the variables directly, or must I assign their properties individually?


By : Anton Malyshev
Date : March 29 2020, 07:55 AM
To fix the issue you can do Delphi classes are reference types. That means that when you define a variable whose type is a class, what you actually have is a reference, or pointer, to the object. And that makes the meaning of the assignment operator := be reference assignment rather than value assignment.
Suppose you have the following declarations:
code :
var
  o1, o2: TObject;
....
o1 := TObject.Create;
o2 := o1;
cds2.CommandText := cds1.CommandText;
cds2 := cds1;
assign many values nested in an object from the parent assignment in Object.assign

assign many values nested in an object from the parent assignment in Object.assign


By : nancy
Date : March 29 2020, 07:55 AM
I wish did fix the issue. That code does not do what you want, and does not work the way you think it does. Notice that you are accidentally introducing global variables, and your computed property key will be the useless and unused "[object CSSStyleDeclaration]". It just does have the desired effect because Object.assign(style, …) is evaluted, but doing it in the nested object has no impact.
You should just write
code :
var card = document.createElement('div');
Object.assign(card, {
    id:'cards',
    innerHTML:'hello world'
});
var style = card.style;
Object.assign(style, {
    width:"300px",
    margin:'auto',
    color:'green',
    height:'300px',
});

var body = document.querySelector('body');
body.appendChild(cards); // probably not necessary, cards already is part of the document
var card = document.createElement('div');
card.id = 'cards';
card.innerHTML = 'hello world';
var style = card.style;
style.width = "300px";
style.margin = 'auto';
style.color = 'green';
style.height = '300px';
_temp1 = card=document.createElement('div'); // global variable!
_temp2 = style=card.style; // global variable!
_temp3 = {
    id:'cards',
    innerHTML:'hello world'
};
_temp4 = style;
_temp5 = {
    width:"300px",
    margin:'auto',
    color:'green',
    height:'300px',
};
for (p in _temp5) // the Object.assign(style, {…})
    _temp4[p] = _temp5[p];

_temp3[String(style)] = [_temp4]; // WTF

for (p in _temp2) // the first part of Object.assign(card, style, …)
    _temp1[p] = _temp2[p]; // WTF
for (p in _temp3) // the second part of Object.assign(card, …, {…})
    _temp1[p] = _temp3[p];

var cards = _temp1;

var body = document.querySelector('body');
body.appendChild(cards);
Using Object.assign() to assign a number results in the object reference being undefined

Using Object.assign() to assign a number results in the object reference being undefined


By : houchang
Date : March 29 2020, 07:55 AM
I wish this help you This has nothing to do with doubles versus integers. It's just that your code
code :
mark ? mark.s += seconds : Object.assign(cumulativeTimes, { [marker]: { s: seconds } } ) // <-- It's a trap!
mark ? mark.ms += milliSeconds : Object.assign(cumulativeTimes, { [marker]: { ms: milliSeconds } } )
if (mark)
   mark.s += seconds;
else
   cumulativeTimes[marker] = { s: seconds };
if (mark)
   mark.ms += milliSeconds;
else
   cumulativeTimes[marker] = { ms: milliSeconds };
if (mark) {
    mark.s += seconds;
    mark.ms += milliSeconds;
} else {
    cumulativeTimes[marker] = {
        s: seconds,
        ms: milliSeconds
    };
}
unable to assign a value in ngFor loop: cannot assign to readonly property of object

unable to assign a value in ngFor loop: cannot assign to readonly property of object


By : Ant Skelton
Date : March 29 2020, 07:55 AM
should help you out You can't achieve directly! But still you can use function and call that function from html by passing the status. I have created a stackblitz for that! Take a look at it! https://stackblitz.com/edit/angular-a7bxve
In html...
code :
<table>
   <tr *ngFor="let d of list">
      <td>{{showStatus(d.desc)}}</td>
   </tr>
</table>
showStatus(status) {
   this.status = status;
}
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