CODEWITHSUNDEEP
c#constructor
Tim Huber
Tim Huber

Reputation: 33

Constructor is not called

public class Unit
{
    public int UnitId { get; set; }
    public Engine EngineStuff { get; set; }

}
public class Engine
{
    public int PS { get; set; }
    public int MaxSpeed { get; set; }
}

var unit = new Unit();
unit.UnitId = 3; //OK because Unit-constructor was called
unit.EngineStuff.PS = 200; //error, because EngineStuff-constructor obviously wasn't called.

How can this "inner" constructor be called? I thought it initializes it automatically?

How can I simply assign a value to the property "EngineStuff.PS"?

Upvotes: 3

Views: 75

Answers (5)

Yves
Yves

Reputation: 3902

Addition to other answers, you can define a getter property to create the instance when you need it first time:

public class Unit
{
    public int UnitId { get; set; }

    private Engine engineStuff;
    public Engine EngineStuff
    {
        get
        {
            if (engineStuff == null) engineStuff = new EngineStuff();
            return engineStuff;
        }
    }
}

Upvotes: 0

Rahul
Rahul

Reputation: 77926

No, you need to set it explicitly like below cause EngineStuff is of type Engine and so you will have instantiate it first before accessing any of it's member.

 unit.EngineStuff = new Engine { PS = 10, MaxSpeed = 2000 };

(OR) you can change your Unit class to have EngineStuff as a getter property and have the instance created there like below

    public Engine EngineStuff 
    { 
        get 
        {
            return new Engine();
        }
    }

Then you can access it 

        var unit = new Unit();
        unit.UnitId = 3;
        unit.EngineStuff.PS = 100;

Upvotes: 2

Saifeddine M
Saifeddine M

Reputation: 493

Simply you need to initialize EngineStuff in either Unit constructor or just before using it.

public class Unit
{
    public Unit()
    {
        EngineStuff = new Engine();
    }
    public int UnitId { get; set; }
    public Engine EngineStuff { get; set; }

}

Or :

var unit = new Unit();
unit.UnitId = 3;
unit.EngineStuff = new Engine():
unit.EngineStuff.PS = 200;

Upvotes: 4

abatishchev
abatishchev

Reputation: 100358

You have to instantiate object's properties explicitly:

public class Unit
{
    public Unit()
    {
        EngineStuff = new Engine();
    }
}

Or if you want to manually control when to instantiate:

var unit = new Unit();
unit.UnitId = 3; 
unit.EngineStuff = new Engine();
unit.EngineStuff.PS = 200;

or simpler:

var unit = new Unit { UnitId = 3 };
unit.EngineStuff = new Engine { PS = 200 };

Upvotes: 4

JohnnyHK
JohnnyHK

Reputation: 312129

EngineStuff is just a reference, you need to set its value to an Engine object that you create, either in the Unit constructor, a property initializer, or plain code.

So either:

// Constructor
public class Unit
{
    public Unit() { EngineStuff = new Engine(); }
    public int UnitId { get; set; }
    public Engine EngineStuff { get; set; }
}

Or

// Property initializer
var unit = new Unit
{
    UnitId = 3,
    EngineStuff = new Engine { PS = 200 }
};

Or

// Plain code
var unit = new Unit();
unit.UnitId = 3;
unit.EngineStuff = new Engine { PS = 200 };

Upvotes: 2

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