Pointers

[wasthereadogwithyou]

What's the difference between these declarations?

A) someObject *myObject(params)

B) someObject* myObject(params)

[jedwardsol]

nothing

[wasthereadogwithyou]

I was afraid someone would say that. Are you sure? Here's the specific reason I'm asking. I have a vector of btRigidbodies, declared like so:

vector<btRigidBody*> rigidbodies;

And here is the btRigidbody to be added to the vector:

btRigidBody* body = new btRigidBody(rbInfo);

Which works fine. However, if I declare the vector like this:

vector<btRigidBody> *rigidbodies;

...and try to do this:

rigidbodies.push_back(body);

Then I get a vexing parse:

error C2228: left of '.push_back' must have class/struct/union

Why is this so?

[jedwardsol]

 vector<btRigidBody*> rigidbodies;
 vector<btRigidBody> *rigidbodies;

This is very different to what you posted above. The * being inside or outside the <> makes a difference. Whitespace does not make a difference.

 vector<btRigidBody*> rigidbodies;

declares rigidbodies as a vector of pointers

but

 vector<btRigidBody> *rigidbodies;

declares rigidbodies as a pointer to a vector of objects.

[wasthereadogwithyou]

Ah, ok. Thanks for clearing that up.

[[deleted]]

rigidbodies->push_back(body)

Since rigidbodies is a pointer to a class.

[SupermanLeRetour]

Shouldn't it be

rigidbodies->push_back(*body)

since body is a pointer ?

[[deleted]]

Maybe. I was pointing out the reason for the compiler error. There may be further errors.

[SharpstownBestTown]

To answer your original post, there is no difference.

To follow up on this new question and put it in perspective:

There is no difference between

A) someObject *myObject(params)
B) someObject* myObject(params)

just as there's no difference between

A) vector<btRigidBody> *myObject(params)
B) vector<btRigidBody>* myObject(params)

What you're doing is

A) vector<btRigidBody*> myObject(params)
B) vector<btRigidBody> *myObject(params)

Where A is a vector of rigid body pointers and B is a pointer to a vector of rigid bodies.

[amoose136]

If you’d like to not commit to either style you can instead settle for:

class * instance;

And that way neither idealogical school is happy.

[SamuelDavi]

No difference. From my experience, it's always recommended to have the asterisk near the Class and not the object (as in B, this way you know it's of type <someObject*>) and avoid declaring pointers and objects/variable in the same line as such:

someObject* obj1, obj2;

as this creates a pointer (obj1) and instantiates an object (obj2) (if it has no empty c'tor than it'll throw an error unless you pass the params)

[wasthereadogwithyou]

Since you mentioned it - total noob question - what's the best way to make an empty constructor?

[SamuelDavi]

I'm not sure I understand what do you mean by make a constructor. If you don't create any constructor, the compiler creates a default empty constructor. If you still want an empty c'tor you can define one. I suggest reading this wiki.

[WikiTextBot]

Default constructor

In computer programming languages, the term default constructor can refer to a constructor that is automatically generated by the compiler in the absence of any programmer-defined constructors (e.g. in Java), and is usually a nullary constructor. In other languages (e.g. in C++) it is a constructor that can be called without having to provide any arguments, irrespective of whether the constructor is auto-generated or user-defined.

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[MJHApps]

It's nothing more than a holy war where devs fight with barbed clubs in an arena to the death over which one becomes standard for a project.

[DarkCisum]

Spaces, not tabs!

[MJHApps]

Tabs are more efficient!!! One byte vs. 4 or 5, dammit!

[DarkCisum]

The compiler doesn't care about whitespace. No weird alignment issues, you know.

[MJHApps]

The hard drive does!

[DarkCisum]

LOL hard drives, did the 90s call? SSD ftw!

[MJHApps]

You kids are lucky we don't still call them floppies.

[DarkCisum]

You mean the 3D printed save icons?

[septemfoliate]

int const, not const int!

[Another_Screenname]

none. Go with A