C + + Reference variables

Reference Variable

use of reference variables in C + +: Definition: int rate=80; int & Pt=rate 1.pt is a reference variable that must be initialized when a variable is referenced. The value of PT and rate points to the same memory variable. The most useful reference is as a function parameter (struct and object). By referencing variables as arguments, you can use the original data instead of the copy. 2. The feature of the reference is closer to the const pointer, which, once associated with a variable, will always be loyal to it, can be initialized to set the reference, but cannot be set by assigning a value int other=30; Pt=other; at this point, the value of rate and the value of PT are changed to 30 but the address is the original rate. Instead of the other address. 3. If the program does not want to change the information passed to it, but wants to use a reference, then you should use a constant reference int Test (const int & P)//when the P-value is changed, the compiler will generate the wrong message 4. If the arguments and application parameters do not match, C + + will generate temporary variables for this, which is allowed only when the parameter is a const reference, and a temporary variable is generated in the following cases, and the function argument references the variable. * * * * * * When a parameter is not a const reference, if it is not an lvalue (and cannot generate a temporary variable) it will result in a compilation error * * * * (emphasis on the 3rd, that is, const) the. argument is of the correct type, but is not an lvalue the. Argument type is incorrect, but can be converted to the correct type Lvalue Concept: Data objects that can be referenced in addition to literal constants and expressions that contain a polynomial 5. Try to declare the reference returned by the function as const so that you do not modify its value by returning the reference. The return reference is actually the alias that returns the referenced variable const sysop & Use (sysop & pref) sysop pref={}; sysop test=use (pref); equivalent User (pref); Test=pref; 6. Inheritance is characterized by a reference to a base class that can point to a derived class object without forcing a type conversion. The benefit is that you can define a function that accepts a base class reference to a seat parameter, which can either use a base class object as an argument or a derived class as a parameter principle of Use: for functions that are passed by value without modification: . Data objects are small and pass by value If the data object is an array, a pointer to the const is defined If the data object is a large structure, you can use the const pointer or the COSNT reference. if it is a class object, use a const reference. for functions that modify values if it is built-in data, use the pointer . Arrays, you can only use pointers . Structure using pointers or references . Object. Using References

C + + reference variable (GO)