问题
I decided one day to create a class in c++ with storage capabilities similar to that of NSMutableArray in objective c (I know vectors are the goto data type for this sort of thing but I made my own anyway). So I made a mutableArray class in c++, and so far it works great. I can add and remove objects, insert them to a specific index if I want, all without having to specify the size of my array.
So my problem is: so far, it can only store objects of type int. Is there any way I can make it so it holds other datatypes without having to create a whole new class for that specific type? I'm not interested in being able to store objects of different datatypes in the same mutableArray, I just want to be able to specify what datatype my mutableArray holds.
My header file:
#define MUTABLEARRAY_H
class mutableArray
{
public:
mutableArray();
virtual ~mutableArray();
void initWithSize(int length);
void initWithArrayThroughIndeces(int nums[], int minimum, int maximum);
void addObject(int number);
void insertObjectAtIndex(int number, int index);
void changeSize(int length);
void removeLastObject();
void removeObjectAtIndex(int index);
int objectAtIndex(int index);
int lastObject();
int firstObject();
int countObjects();
protected:
private:
int *start;
int amount;
};
#endif // MUTABLEARRAY_H
my cpp file:
#include "mutableArray.h"
mutableArray::mutableArray()
{
//ctor
start = new int;
amount = 0;
}
mutableArray::~mutableArray()
{
//dtor
}
void mutableArray::initWithSize(int length){
amount = length;
}
void mutableArray::initWithArrayThroughIndeces(int nums[], int minimum, int maximum){
amount = maximum - minimum;
start = nums + minimum;
}
void mutableArray::addObject(int number){
amount++;
start[amount] = number;
}
void mutableArray::insertObjectAtIndex(int number, int index){
amount++;
int j = 0;
for (int *i = start + amount; i > start; i--){
if (j >= index){
start[j + 1] = *i;
}
j++;
}
start[index] = number;
}
void mutableArray::removeLastObject(){
amount--;
}
void mutableArray::removeObjectAtIndex(int index){
amount--;
int j = 0;
for (int *i = start; i < start + amount; i++){
if (j != index){
start[j] = *i;
j++;
}
}
}
int mutableArray::objectAtIndex(int index){
return start[index];
}
int mutableArray::lastObject(){
return start[amount];
}
int mutableArray::firstObject(){
return *start;
}
int mutableArray::countObjects(){
return amount;
}
So there it is. Any help will be much appreciated.
回答1:
This will answer your question
class template
here is an example of how I implemented a part of vector class using template
This is one file vector.h
#ifndef VECTOR_H
#define VECTOR_H
#include <iostream>
#include<stdlib.h>
#include<malloc.h>
template <typename T>
class Vector{
private:
T *buffer;
int threshold;
int length;
void Allocate();
void ReAllocate(int);
public:
Vector();
~Vector();
void push_back (const T& val);
void pop_back();
void clear(void);
void erase (int position);
void erase (int first, int last);
int capacity() const;
int size() const;
T* at(int n) const;
T& operator[] (int n) const;
};
template <typename T>
Vector<T>:: Vector(){
buffer=NULL;
length=0;
threshold=10;
Allocate();
}
template <typename T>
void Vector<T>::Allocate(){
buffer = (T*)(malloc(threshold*sizeof(T)));
}
template <typename T>
void Vector<T>::ReAllocate(int size_x){
std::cout<<"In buffer realloc"<<std::endl;
threshold=threshold+size_x;
buffer = (T*)(realloc(buffer,(sizeof(T))*threshold));
}
template <typename T>
void Vector<T>::push_back (const T& val){
if(length<threshold){
buffer[length]=val;
std::cout<<buffer[length]<<std::endl;
length++;
}
else{
ReAllocate(10);
push_back(val);
}
}
template <typename T>
void Vector<T>::erase (int first, int last){
T *tempBuffer=buffer;
if(first>=0&&last<length){
int count=0;
for(int i=0;i<length;i++){
if(i<first||i>last){
buffer[count]=buffer[i];
count++;
}
}
length=count;
}else{
// illegal params
}
}
template <typename T>
void Vector<T>::erase(int position){
if(position>=0&&position<length){
int count=0;
for(int i=0;i<length;i++){
if(i!=position-1){
buffer[count]=buffer[i];
count++;
}
}
length--;
}else{
// illegal params
}
}
template <typename T>
Vector<T>:: ~Vector(){
free(buffer);
length=0;
threshold=10;
Allocate();
}
template <typename T>
int Vector<T>::capacity() const{
return threshold;
}
template <typename T>
int Vector<T>::size() const{
return length;
}
template <typename T>
T* Vector<T>::at(int n) const{
if(n>0&&n<length){
return &buffer[n];
}
else return NULL;
}
template<typename T>
void Vector<T>::clear(void){
buffer[length]=0;
length=0;
}
template<typename T>
T& Vector<T>::operator[](int n) const{
if(n>0&&n<length){
return buffer[n];
}
}
#endif
This is another file using my vetcor class
#include"Vector.h"
#include<iostream>
int main(){
Vector<int> vec;
vec.push_back(2);
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);
vec.push_back(2);
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);
vec.push_back(2);
vec.push_back(3);
vec.push_back(4);
vec.push_back(5);
vec.erase(1);
std::cout<<vec.capacity()<<std::endl;
std::cout<<vec.size()<<std::endl;
int* a=vec.at(2);
std::cout<<"Element At 2 is :"<<*a<<std::endl;
std::cout<<"Element At 2 using [] operator :"<<vec[5]<<std::endl;
return 0;
}
So the way I created Vector<int> in main in the similar manner by just writing Vector<char> you will have vector of characters. Note: header files are never compiled
来源：https://stackoverflow.com/questions/17715810/c-mutable-array-of-various-data-types