CODEWITHSUNDEEP
c#classobject
user2926430
user2926430

Reputation: 391

How to access methods from an object of type object

I have two classes named Road and City, they have the following methods:

"class Road"

public Road()
    {
      public int getId()
      {
          return this.id;
      }
    }

"class City"

public City()
    {
      public string getName()
      {
          return this.name;
      }
    }

In another class named Image, I create instances of City and Road of the type Object

Example

    Object o = new Object();
    City c = cc.getCityByCoordinates(coordinates);
    o = c;

Now how can I access the methods from City.class on the "o" object? Like o.getName(); - If that is even possible, please help.

Upvotes: 0

Views: 167

Answers (4)

AWinkle
AWinkle

Reputation: 673

You can also use reflection to retrieve the result off of City.

        MethodInfo mi = c.GetType().GetMethod("getName");
        var result = mi.Invoke(o, null).ToString()

Upvotes: 0

Chris Hinton
Chris Hinton

Reputation: 866

City cityFromObject = o as City;
if(null != cityFromObject) {
   // do something with cityFromObject.getName();
}

Upvotes: 1

BradleyDotNET
BradleyDotNET

Reputation: 61349

You can easily do this by casting to "City":

City c = o as City;
c.getName();

Note that the as operator will return null if the cast is invalid, so you should check before using it:

City c = o as City;
if (c != null)
    c.getName();

The other way is to use the is operator and a C-style cast:

if (o is City)
   ((City)o).getName();

A word of warning, downcasting like this is a "code smell". Look at your code and see why you need to do this. Perhaps it should be stored in an interface instead. Object variables can also be a "code smell", and used only if necessary.

Upvotes: 5

D Stanley
D Stanley

Reputation: 152556

How can I access the methods from City class on the "o" object?

Cast it:

Object o = new Object();
City c = cc.getCityByCoordinates(coordinates);
o = c;
string name = ((City)o).getName();

If o is not really a City then you'll get an exception at run-time. To check if o is a City before trying to cast it, you can use as:

City c2 = o as City;  // c2 will be `null` if o is not castable to City
if(c2 != null)
   string name = c2.getName();

Upvotes: 3

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