How can I overload = operator for 'MyClass object = f(x)'?
As in title.
I have problem with operator overload.
int variable = 5;
int* f() {
return &variable;
}
class MyClass {
public:
int* i;
MyClass operator=(int* j) {
MyClass x;
x.i=j;
return x;
}
};
If I try to make my object like this:
MyClass m=f();
it doesn't work. But this:
MyClass m;
m=f();
works...
c++
add a comment |
As in title.
I have problem with operator overload.
int variable = 5;
int* f() {
return &variable;
}
class MyClass {
public:
int* i;
MyClass operator=(int* j) {
MyClass x;
x.i=j;
return x;
}
};
If I try to make my object like this:
MyClass m=f();
it doesn't work. But this:
MyClass m;
m=f();
works...
c++
Youroperator()
is creating a newMyClass
and return it. You should mutate the current object.
– Guillaume Racicot
Jan 1 at 18:04
I modified it to:this->i=j; return *this;
. Is it better now?
– Filip Krawczyk
Jan 1 at 18:10
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14
add a comment |
As in title.
I have problem with operator overload.
int variable = 5;
int* f() {
return &variable;
}
class MyClass {
public:
int* i;
MyClass operator=(int* j) {
MyClass x;
x.i=j;
return x;
}
};
If I try to make my object like this:
MyClass m=f();
it doesn't work. But this:
MyClass m;
m=f();
works...
c++
As in title.
I have problem with operator overload.
int variable = 5;
int* f() {
return &variable;
}
class MyClass {
public:
int* i;
MyClass operator=(int* j) {
MyClass x;
x.i=j;
return x;
}
};
If I try to make my object like this:
MyClass m=f();
it doesn't work. But this:
MyClass m;
m=f();
works...
c++
c++
asked Jan 1 at 17:52
Filip KrawczykFilip Krawczyk
31
31
Youroperator()
is creating a newMyClass
and return it. You should mutate the current object.
– Guillaume Racicot
Jan 1 at 18:04
I modified it to:this->i=j; return *this;
. Is it better now?
– Filip Krawczyk
Jan 1 at 18:10
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14
add a comment |
Youroperator()
is creating a newMyClass
and return it. You should mutate the current object.
– Guillaume Racicot
Jan 1 at 18:04
I modified it to:this->i=j; return *this;
. Is it better now?
– Filip Krawczyk
Jan 1 at 18:10
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14
Your
operator()
is creating a new MyClass
and return it. You should mutate the current object.– Guillaume Racicot
Jan 1 at 18:04
Your
operator()
is creating a new MyClass
and return it. You should mutate the current object.– Guillaume Racicot
Jan 1 at 18:04
I modified it to:
this->i=j; return *this;
. Is it better now?– Filip Krawczyk
Jan 1 at 18:10
I modified it to:
this->i=j; return *this;
. Is it better now?– Filip Krawczyk
Jan 1 at 18:10
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14
add a comment |
1 Answer
1
active
oldest
votes
That first example does not use operator=
(yes, even though there is a =
symbol!).
As it is a declaration/definition/initialization, it uses the constructor.
You may create a constructor to do what you need. This ought to be described in your C++ book.
By the way, your operator=
is implemented weirdly. You're supposed to modify the current object, not create and return a new one. Again, refer to your book for the proper way of doing this.
add a comment |
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
That first example does not use operator=
(yes, even though there is a =
symbol!).
As it is a declaration/definition/initialization, it uses the constructor.
You may create a constructor to do what you need. This ought to be described in your C++ book.
By the way, your operator=
is implemented weirdly. You're supposed to modify the current object, not create and return a new one. Again, refer to your book for the proper way of doing this.
add a comment |
That first example does not use operator=
(yes, even though there is a =
symbol!).
As it is a declaration/definition/initialization, it uses the constructor.
You may create a constructor to do what you need. This ought to be described in your C++ book.
By the way, your operator=
is implemented weirdly. You're supposed to modify the current object, not create and return a new one. Again, refer to your book for the proper way of doing this.
add a comment |
That first example does not use operator=
(yes, even though there is a =
symbol!).
As it is a declaration/definition/initialization, it uses the constructor.
You may create a constructor to do what you need. This ought to be described in your C++ book.
By the way, your operator=
is implemented weirdly. You're supposed to modify the current object, not create and return a new one. Again, refer to your book for the proper way of doing this.
That first example does not use operator=
(yes, even though there is a =
symbol!).
As it is a declaration/definition/initialization, it uses the constructor.
You may create a constructor to do what you need. This ought to be described in your C++ book.
By the way, your operator=
is implemented weirdly. You're supposed to modify the current object, not create and return a new one. Again, refer to your book for the proper way of doing this.
answered Jan 1 at 17:53
Lightness Races in OrbitLightness Races in Orbit
292k52475808
292k52475808
add a comment |
add a comment |
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Your
operator()
is creating a newMyClass
and return it. You should mutate the current object.– Guillaume Racicot
Jan 1 at 18:04
I modified it to:
this->i=j; return *this;
. Is it better now?– Filip Krawczyk
Jan 1 at 18:10
@FilipKrawczyk Much better - it should also return by reference otherwise it's still a fresh object you're returning, which breaks chaining in subtle ways.
– Lightness Races in Orbit
Jan 1 at 20:14