Difference between revisions of "cpp/memory/unique ptr/make unique"
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< cpp | memory | unique ptr
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struct Vec3 | struct Vec3 | ||
{ | { | ||
| − | + | int x; | |
| − | + | int y; | |
| − | + | int z; | |
| − | + | Vec3() :x(0), y(0), z(0) | |
| − | + | { | |
| + | } | ||
| − | + | Vec3(int x, int y, int z) :x(x), y(y), z(z) | |
| + | { | ||
| + | } | ||
| − | + | friend std::ostream& operator<<(std::ostream& os, Vec3& v); | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
}; | }; | ||
std::ostream& operator<<(std::ostream& os, Vec3& v) | std::ostream& operator<<(std::ostream& os, Vec3& v) | ||
{ | { | ||
| − | + | return os << "x:" << v.x << " y:" << v.y << " z:" << v.z << '\n'; | |
} | } | ||
auto main() -> int | auto main() -> int | ||
{ | { | ||
| − | + | // Use the default constructor. | |
| − | + | std::unique_ptr<Vec3> v1 = std::make_unique<Vec3>(); | |
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | // Use the constructor that matches these arguments | |
| + | std::unique_ptr<Vec3> v2 = std::make_unique<Vec3>(0, 1, 2); | ||
| − | + | // Create a unique_ptr to an array of 5 elements | |
| + | std::unique_ptr<Vec3[]> v3 = std::make_unique<Vec3[]>(5); | ||
| − | + | std::cout << "make_unique<Vec3>():" << '\n' | |
| − | + | std::cout << (*v1) << '\n'; | |
| − | + | std::cout << "make_unique<Vec3>(0,1,2):" << '\n'; | |
| − | + | std::cout << (*v2) << '\n'; | |
| − | + | std::cout << "make_unique<Vec3[]>(5):" << '\n'; | |
| − | + | for (int i = 0; i < 5; i++) { | |
| − | + | std::cout << v3[i] << '\n'; | |
| − | std::cout << | + | } |
| − | + | ||
| − | + | return 0; | |
} | } | ||
| output= | | output= | ||
Revision as of 04:31, 21 September 2014
| Defined in header <memory>
|
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| template< class T, class... Args > unique_ptr<T> make_unique( Args&&... args ); |
(1) | (since C++14) (only for non-array types) |
| template< class T > unique_ptr<T> make_unique( std::size_t size ); |
(2) | (since C++14) (only for array types with unknown bound) |
| template< class T, class... Args > /* unspecified */ make_unique( Args&&... args ) = delete; |
(3) | (since C++14) (only for array types with known bound) |
Constructs an object of type T and wraps it in a std::unique_ptr.
1) Constructs a non-array type
T. The arguments args are passed to the constructor of T. The function does not participate in the overload resolution if T is an array type. The function is equivalent to:
unique_ptr<T>(new T(std::forward<Args>(args)...))
2) Constructs an array of unknown bound
T. The function does not participate in the overload resolution unless T is an array of unknown bound. The function is equivalent to:
unique_ptr<T>(new typename std::remove_extent<T>::type[size]())
3) Construction of arrays of known bound is disallowed.
Contents |
Parameters
| args | - | list of arguments with which an instance of T will be constructed.
|
| size | - | the size of the array to construct |
Return value
std::unique_ptr of an instance of type T.
Exceptions
Any exception thrown by the contructor of T. If an exception is thrown, this function has no effect.
Example
Run this code
#include <iostream> #include <memory> struct Vec3 { int x; int y; int z; Vec3() :x(0), y(0), z(0) { } Vec3(int x, int y, int z) :x(x), y(y), z(z) { } friend std::ostream& operator<<(std::ostream& os, Vec3& v); }; std::ostream& operator<<(std::ostream& os, Vec3& v) { return os << "x:" << v.x << " y:" << v.y << " z:" << v.z << '\n'; } auto main() -> int { // Use the default constructor. std::unique_ptr<Vec3> v1 = std::make_unique<Vec3>(); // Use the constructor that matches these arguments std::unique_ptr<Vec3> v2 = std::make_unique<Vec3>(0, 1, 2); // Create a unique_ptr to an array of 5 elements std::unique_ptr<Vec3[]> v3 = std::make_unique<Vec3[]>(5); std::cout << "make_unique<Vec3>():" << '\n' std::cout << (*v1) << '\n'; std::cout << "make_unique<Vec3>(0,1,2):" << '\n'; std::cout << (*v2) << '\n'; std::cout << "make_unique<Vec3[]>(5):" << '\n'; for (int i = 0; i < 5; i++) { std::cout << v3[i] << '\n'; } return 0; }
Output:
make_unique<Vec3>(): x:0 y:0 z:0 make_unique<Vec3>(0,1,2): x:0 y:1 z:2 make_unique<Vec3[]>(5): x:0 y:0 z:0 x:0 y:0 z:0 x:0 y:0 z:0 x:0 y:0 z:0 x:0 y:0 z:0
See also
constructs a new unique_ptr (public member function) |
