string类的基本函数编写

class String
{
public:
String(const char *str=NULL);
String(const String &otherdata);
~String(void);
String &operator=(const String &otherdata);
outputString();
private:
char *input_data;
};
String::~String()
{
delete[]input_data;//destructor析构函数，释放地址空间
}
String::(const String &otherdata)
{
assert(str!=NULL);
if(str==NULL)
{
inputdata=new char[1];
*inputdata='\0';
}
else
{
int length=strlen(otherdata.inputdata);
inputdata=new char[length];
strcpy(inputdata,otherdata.inputdata);
}
}
String::(const)