Vector size is not correct - how can we initialize a vector inside a structure
-3
I have below sample code:
#include <iostream>
#include <vector>
typedef struct defs
{
std::vector<int> myvec;
} dvec;
typedef struct devdef: public dvec
{
dvec dvec1;
devdef()
{
dvec1.myvec.push_back(10);
}
}myVec;
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Compile and execute:
$ c++ -std=c++11 try58.cpp
$ ./a.exe
my vec size is 0
I was expecting the size of vector to be 1 - why the same is 0?
c++ c++11
asked Nov 12 at 14:58
Programmer
2,8341649102
|
show 2 more comments
-3
I have below sample code:
#include <iostream>
#include <vector>
typedef struct defs
{
std::vector<int> myvec;
} dvec;
typedef struct devdef: public dvec
{
dvec dvec1;
devdef()
{
dvec1.myvec.push_back(10);
}
}myVec;
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Compile and execute:
$ c++ -std=c++11 try58.cpp
$ ./a.exe
my vec size is 0
I was expecting the size of vector to be 1 - why the same is 0?
c++ c++11
asked Nov 12 at 14:58
Programmer
2,8341649102
8
What's up with thosetypedef's everywhere? You don't need them
– Rakete1111
Nov 12 at 14:59
5
Such confusion, much wow
– Zereges
Nov 12 at 15:01
4
@Programmer That's a style used in c becausestructdoesn't define a type name there. In c++ you don't need totypedefthem sincestructcreate type names.
– François Andrieux
Nov 12 at 15:01
2
dvec1.myvec.push_back(10);pushes data to a different vector, than you are trying to reference inv1.myvec.size().
– Algirdas Preidžius
Nov 12 at 15:02
1
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05
|
show 2 more comments
-3
-3
-3
I have below sample code:
#include <iostream>
#include <vector>
typedef struct defs
{
std::vector<int> myvec;
} dvec;
typedef struct devdef: public dvec
{
dvec dvec1;
devdef()
{
dvec1.myvec.push_back(10);
}
}myVec;
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Compile and execute:
$ c++ -std=c++11 try58.cpp
$ ./a.exe
my vec size is 0
I was expecting the size of vector to be 1 - why the same is 0?
c++ c++11
asked Nov 12 at 14:58
Programmer
2,8341649102
I have below sample code:
#include <iostream>
#include <vector>
typedef struct defs
{
std::vector<int> myvec;
} dvec;
typedef struct devdef: public dvec
{
dvec dvec1;
devdef()
{
dvec1.myvec.push_back(10);
}
}myVec;
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Compile and execute:
$ c++ -std=c++11 try58.cpp
$ ./a.exe
my vec size is 0
I was expecting the size of vector to be 1 - why the same is 0?
c++ c++11
c++ c++11
asked Nov 12 at 14:58
Programmer
2,8341649102
asked Nov 12 at 14:58
Programmer
2,8341649102
edited Nov 12 at 14:59
asked Nov 12 at 14:58
Programmer
2,8341649102
asked Nov 12 at 14:58
Programmer
2,8341649102
asked Nov 12 at 14:58
Programmer
2,8341649102
2,8341649102
8
What's up with thosetypedef's everywhere? You don't need them
– Rakete1111
Nov 12 at 14:59
5
Such confusion, much wow
– Zereges
Nov 12 at 15:01
4
@Programmer That's a style used in c becausestructdoesn't define a type name there. In c++ you don't need totypedefthem sincestructcreate type names.
– François Andrieux
Nov 12 at 15:01
2
dvec1.myvec.push_back(10);pushes data to a different vector, than you are trying to reference inv1.myvec.size().
– Algirdas Preidžius
Nov 12 at 15:02
1
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05
|
show 2 more comments
8
What's up with thosetypedef's everywhere? You don't need them
– Rakete1111
Nov 12 at 14:59
5
Such confusion, much wow
– Zereges
Nov 12 at 15:01
4
@Programmer That's a style used in c becausestructdoesn't define a type name there. In c++ you don't need totypedefthem sincestructcreate type names.
– François Andrieux
Nov 12 at 15:01
2
dvec1.myvec.push_back(10);pushes data to a different vector, than you are trying to reference inv1.myvec.size().
– Algirdas Preidžius
Nov 12 at 15:02
1
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05
8
8
What's up with those
typedef's everywhere? You don't need them– Rakete1111
Nov 12 at 14:59
What's up with those
typedef's everywhere? You don't need them– Rakete1111
Nov 12 at 14:59
5
5
Such confusion, much wow
– Zereges
Nov 12 at 15:01
Such confusion, much wow
– Zereges
Nov 12 at 15:01
4
4
@Programmer That's a style used in c because
struct doesn't define a type name there. In c++ you don't need to typedef them since struct create type names.– François Andrieux
Nov 12 at 15:01
@Programmer That's a style used in c because
struct doesn't define a type name there. In c++ you don't need to typedef them since struct create type names.– François Andrieux
Nov 12 at 15:01
2
2
dvec1.myvec.push_back(10); pushes data to a different vector, than you are trying to reference in v1.myvec.size().– Algirdas Preidžius
Nov 12 at 15:02
dvec1.myvec.push_back(10); pushes data to a different vector, than you are trying to reference in v1.myvec.size().– Algirdas Preidžius
Nov 12 at 15:02
1
1
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05
|
show 2 more comments
2 Answers
2
active
oldest
votes
0
This version, I think, does what you wanted.
#include <iostream>
#include <vector>
struct dvec
{
std::vector<int> myvec;
}
struct myVec : public dvec
{
myVec()
{
myvec.push_back(10);
}
}
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Some notes about what I've changed.
- There's no need to use a
typedefto create a new type. In C++ bothclassandstructdefine new types. - When deriving the new type
myVecfromdvec, it contains the vectrormyvec, so there is no need to add a new one. - In the constructor for the derived type
myVec, we can access themyvecmember of the base type directly, since it is a member of this object.
answered Nov 12 at 15:19
Tim Randall
1,9221119
add a comment |
2
You have dvecs as both a parent to myVec as well as a member of myVec. In your constructor you push a value to dvec1.myvec, but in A you read v1.myvec aka the member of the parent. You simply have two instances of dvecs in your structure and you're using different ones in your functions.
answered Nov 12 at 15:03
Kiskae
12.3k12538
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
0
This version, I think, does what you wanted.
#include <iostream>
#include <vector>
struct dvec
{
std::vector<int> myvec;
}
struct myVec : public dvec
{
myVec()
{
myvec.push_back(10);
}
}
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Some notes about what I've changed.
- There's no need to use a
typedefto create a new type. In C++ bothclassandstructdefine new types. - When deriving the new type
myVecfromdvec, it contains the vectrormyvec, so there is no need to add a new one. - In the constructor for the derived type
myVec, we can access themyvecmember of the base type directly, since it is a member of this object.
answered Nov 12 at 15:19
Tim Randall
1,9221119
add a comment |
0
This version, I think, does what you wanted.
#include <iostream>
#include <vector>
struct dvec
{
std::vector<int> myvec;
}
struct myVec : public dvec
{
myVec()
{
myvec.push_back(10);
}
}
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Some notes about what I've changed.
- There's no need to use a
typedefto create a new type. In C++ bothclassandstructdefine new types. - When deriving the new type
myVecfromdvec, it contains the vectrormyvec, so there is no need to add a new one. - In the constructor for the derived type
myVec, we can access themyvecmember of the base type directly, since it is a member of this object.
answered Nov 12 at 15:19
Tim Randall
1,9221119
add a comment |
0
0
0
This version, I think, does what you wanted.
#include <iostream>
#include <vector>
struct dvec
{
std::vector<int> myvec;
}
struct myVec : public dvec
{
myVec()
{
myvec.push_back(10);
}
}
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Some notes about what I've changed.
- There's no need to use a
typedefto create a new type. In C++ bothclassandstructdefine new types. - When deriving the new type
myVecfromdvec, it contains the vectrormyvec, so there is no need to add a new one. - In the constructor for the derived type
myVec, we can access themyvecmember of the base type directly, since it is a member of this object.
answered Nov 12 at 15:19
Tim Randall
1,9221119
This version, I think, does what you wanted.
#include <iostream>
#include <vector>
struct dvec
{
std::vector<int> myvec;
}
struct myVec : public dvec
{
myVec()
{
myvec.push_back(10);
}
}
class A
{
public:
A():v1()
{
std::cout << "my vec size is " << v1.myvec.size() << std::endl;
}
private:
myVec v1;
};
int main()
{
A a1;
}
Some notes about what I've changed.
- There's no need to use a
typedefto create a new type. In C++ bothclassandstructdefine new types. - When deriving the new type
myVecfromdvec, it contains the vectrormyvec, so there is no need to add a new one. - In the constructor for the derived type
myVec, we can access themyvecmember of the base type directly, since it is a member of this object.
answered Nov 12 at 15:19
Tim Randall
1,9221119
answered Nov 12 at 15:19
Tim Randall
1,9221119
answered Nov 12 at 15:19
Tim Randall
1,9221119
answered Nov 12 at 15:19
Tim Randall
1,9221119
1,9221119
add a comment |
add a comment |
2
You have dvecs as both a parent to myVec as well as a member of myVec. In your constructor you push a value to dvec1.myvec, but in A you read v1.myvec aka the member of the parent. You simply have two instances of dvecs in your structure and you're using different ones in your functions.
answered Nov 12 at 15:03
Kiskae
12.3k12538
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
add a comment |
2
You have dvecs as both a parent to myVec as well as a member of myVec. In your constructor you push a value to dvec1.myvec, but in A you read v1.myvec aka the member of the parent. You simply have two instances of dvecs in your structure and you're using different ones in your functions.
answered Nov 12 at 15:03
Kiskae
12.3k12538
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
add a comment |
2
2
2
You have dvecs as both a parent to myVec as well as a member of myVec. In your constructor you push a value to dvec1.myvec, but in A you read v1.myvec aka the member of the parent. You simply have two instances of dvecs in your structure and you're using different ones in your functions.
answered Nov 12 at 15:03
Kiskae
12.3k12538
You have dvecs as both a parent to myVec as well as a member of myVec. In your constructor you push a value to dvec1.myvec, but in A you read v1.myvec aka the member of the parent. You simply have two instances of dvecs in your structure and you're using different ones in your functions.
answered Nov 12 at 15:03
Kiskae
12.3k12538
answered Nov 12 at 15:03
Kiskae
12.3k12538
answered Nov 12 at 15:03
Kiskae
12.3k12538
answered Nov 12 at 15:03
Kiskae
12.3k12538
12.3k12538
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
add a comment |
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
Thanks after I read v1.dvec1.myvec.size() I was able to get the correct size
– Programmer
Nov 12 at 15:07
add a comment |
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8
What's up with those
typedef's everywhere? You don't need them– Rakete1111
Nov 12 at 14:59
5
Such confusion, much wow
– Zereges
Nov 12 at 15:01
4
@Programmer That's a style used in c because
structdoesn't define a type name there. In c++ you don't need totypedefthem sincestructcreate type names.– François Andrieux
Nov 12 at 15:01
2
dvec1.myvec.push_back(10);pushes data to a different vector, than you are trying to reference inv1.myvec.size().– Algirdas Preidžius
Nov 12 at 15:02
1
I"m upvoting @Zereges because this looks like a bad transition from C to C++. Deriving a new struct from the old, and adding in another member of the same type as that already present in the base.... plus the typedef thing. I think that OP would benefit from some "compare/contrast" tutorials for C programmers moving to C++
– Tim Randall
Nov 12 at 15:05