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Advanced Classes and Objects Part III
Part III Using swap When using moveFrom , if a new data member is added, both swap and moveFrom have to be modified. To avoid that, one can write the move constructor and move assignment operator with a default constructor and the swap function. class Bank { private : Bank ( ) = default ; } Now cleanup() and moveFrom() can be removed. The destructor handles the code from cleanup . The code is as follows: Bank :: Bank ( Bank && src ) noexcept : Bank ( ) { swap ( * this , src ) ; //Default constructor creates *this. } Bank & Bank :: operator = ( Bank && rhs ) noexcept { Bank temp ( std :: move ( rhs ) ) //Need std::move because rhs is named swap ( * this , temp ) ; return * this ; } Implementing swap with move semantics Using move semantics improves the performance of swap as seen below: void swa...
C++ strings and string_view
C-style strings C style strings should be avoided except when interfacing with C libraries. C string library functions provide no bounds checking and memory allocation support. They are represented as an array of characters. Last character of the string is the null character \0 , so that code that uses the string knows where it ends. The space needed for a string is always one more than the number of readable characters. String Literals Strings written with quotes around them are string literals. They are stored in a read-only part of memory. Because they are stored in readonly sections, attempting to modify string literals is undefined behavior . Example: char * str = "world" ; str [ 0 ] = 'y' ; //undefined behavior If the code respected the standard and assigned the string literal to const char* , the compiler will catch attempts to modify string literals: const char * str = "world" ; str [ 0 ] = 'k' ; //compiler will f...
Advanced Classes and Objects Part II
Part II Continuing from Part I, here are the implementations of cleanup , moveFrom , the move constructor and the move assignment operator. void Bank :: cleanup ( ) noexcept { delete [ ] mCheckingAccounts ; mCheckingAccounts = nullptr ; mName = "" ; mNumAccounts = 0 ; } void Bank :: moveFrom ( Bank & src ) noexcept { //Shallow copy first. Move objects. mNumAccounts = src . mNumAccounts ; mCheckingAccounts = src . mCheckingAccounts ; mName = std :: move ( src . mName ) ; //Ownership has moved, reset the source object src . mName = "" ; src . mNumAccounts = 0 ; src . mCheckingAccounts = nullptr ; } //Move constructor Bank :: Bank ( Bank && src ) noexcept { moveFrom ( src ) ; } //Move assignment operator Bank & :: Bank :: operator = ( Bank && rhs ) noexcept { if ( this == & rhs ) { return * this ; } cleanu...
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