constructor

问题 I have the following piece of code: class MyStruct(ctypes.Structure): _fields_= [('id', ctypes.uint), ('perm', ctypes.uint)] When the class is defined, i'm able to copy data from buffer directly on my fields. Eg: ms = MyStruct.from_buffer_copy("\xAA\xAA\xAA\xAA\x11\x11\x11\x11") print ms.id, ms.perm Everythings works fine, here id will be 0xAAAAAAAA and perm equals to 0x11111111 . Now, i tried to do the same thing during the instantiation, with the following code: class MyStruct(ctypes

问题 I have the following piece of code: class MyStruct(ctypes.Structure): _fields_= [('id', ctypes.uint), ('perm', ctypes.uint)] When the class is defined, i'm able to copy data from buffer directly on my fields. Eg: ms = MyStruct.from_buffer_copy("\xAA\xAA\xAA\xAA\x11\x11\x11\x11") print ms.id, ms.perm Everythings works fine, here id will be 0xAAAAAAAA and perm equals to 0x11111111 . Now, i tried to do the same thing during the instantiation, with the following code: class MyStruct(ctypes

问题 I recently read about copy & swap and am now trying to implement the ctors in a base and derived class. I have the four constructors in both my base and derived class, however I am unsure how to implement the assignment operator of the derived class. explicit Base(int i) : m_i{i} {} Base(const Base & other) : m_i{other.m_i} Base(Base && other) : Base(0) { swap(*this, other); } Base & operator=(Base other) { swap(*this, other); return *this; } friend void swap(Base & a, Base & b) noexcept {

问题 I recently read about copy & swap and am now trying to implement the ctors in a base and derived class. I have the four constructors in both my base and derived class, however I am unsure how to implement the assignment operator of the derived class. explicit Base(int i) : m_i{i} {} Base(const Base & other) : m_i{other.m_i} Base(Base && other) : Base(0) { swap(*this, other); } Base & operator=(Base other) { swap(*this, other); return *this; } friend void swap(Base & a, Base & b) noexcept {

问题 I recently read about copy & swap and am now trying to implement the ctors in a base and derived class. I have the four constructors in both my base and derived class, however I am unsure how to implement the assignment operator of the derived class. explicit Base(int i) : m_i{i} {} Base(const Base & other) : m_i{other.m_i} Base(Base && other) : Base(0) { swap(*this, other); } Base & operator=(Base other) { swap(*this, other); return *this; } friend void swap(Base & a, Base & b) noexcept {

问题 I recently read about copy & swap and am now trying to implement the ctors in a base and derived class. I have the four constructors in both my base and derived class, however I am unsure how to implement the assignment operator of the derived class. explicit Base(int i) : m_i{i} {} Base(const Base & other) : m_i{other.m_i} Base(Base && other) : Base(0) { swap(*this, other); } Base & operator=(Base other) { swap(*this, other); return *this; } friend void swap(Base & a, Base & b) noexcept {

问题 I am using the Scala 2.8 default parameters on a constructor, and for Java compatibility reasons, I wanted a no-arg constructor that uses the default parameters. This doesn't work for very sensible reasons: class MyClass(field1: String = "foo", field2: String = "bar") { def this() = { this() // <-- Does not compile, but how do I not duplicate the defaults? } } I am wondering if there is anything that I am missing. Any thoughts that don't require duplicating the parameter defaults? Thanks! 回答1

问题 I am using the Scala 2.8 default parameters on a constructor, and for Java compatibility reasons, I wanted a no-arg constructor that uses the default parameters. This doesn't work for very sensible reasons: class MyClass(field1: String = "foo", field2: String = "bar") { def this() = { this() // <-- Does not compile, but how do I not duplicate the defaults? } } I am wondering if there is anything that I am missing. Any thoughts that don't require duplicating the parameter defaults? Thanks! 回答1

问题 I am using the Scala 2.8 default parameters on a constructor, and for Java compatibility reasons, I wanted a no-arg constructor that uses the default parameters. This doesn't work for very sensible reasons: class MyClass(field1: String = "foo", field2: String = "bar") { def this() = { this() // <-- Does not compile, but how do I not duplicate the defaults? } } I am wondering if there is anything that I am missing. Any thoughts that don't require duplicating the parameter defaults? Thanks! 回答1

问题 I am using the Scala 2.8 default parameters on a constructor, and for Java compatibility reasons, I wanted a no-arg constructor that uses the default parameters. This doesn't work for very sensible reasons: class MyClass(field1: String = "foo", field2: String = "bar") { def this() = { this() // <-- Does not compile, but how do I not duplicate the defaults? } } I am wondering if there is anything that I am missing. Any thoughts that don't require duplicating the parameter defaults? Thanks! 回答1