我正在尝试为我的Geometry类创建一个C ++项目。我希望用户能够存储和访问变量。为此，我创建了一个struct var，其中包含string name和float value。我有一个vector < var > varList来保存变量。但是，在编译时，程序根本不能正常工作......首先，它检查变量“dog”是否存在，它显然不存在，并发现它确实存在。然后它尝试更改变量dog并changeVar，而不是返回ERR_NONEXISTENT，返回正确的退出状态为零。在检查变量时，它看到它不存在。然后，在尝试列出所有变量时，会产生分段错误。见下文：
Building Generator 1.0 Alpha Variable Systems Test ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter a variable name: dog Enter a value (A FLOAT!): 2.2 Checking to see if dog exists. It exists! Changing variable. Function returned 0 Enter a variable to check: dog Variable "dog" doesn't exist! Segmentation fault
我的来源是here。我正在使用Eclipse Helios编译，使用G ++ 4.2.1，在Mac 10.6.7 Snow Leopard上编译。发生了什么事？
如果这不起作用，我会尝试找出std::map ...
另外，这只是我的第二个问题;请原谅（但通知我）任何格式错误。
谢谢，
BF
编辑：这是一些代码：vsystem.cpp
/*
* vsystem.cpp
*
* Created on: Apr 29, 2011
* Author: wjc
*/
#include <string>
#include <vector>
#include <sstream>
#include "vsystem.h"
using namespace std;
vector <var> varList;
int addVar(string varName, float value){
// Check to see if varName already exists
bool varExists = false;
for (unsigned int i=0; i<varList.size(); i++){
if (varList[i].name == varName){
varExists = true;
return ERR_VAR_EXISTS;
}
}
// Good! The variable doesn't exist yet.
var tempVar;
tempVar.name = varName;
tempVar.value = value;
varList.push_back(tempVar);
return 0;
}
int changeVar(string varName, float newValue){
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name != varName){ // If it doesn't match…
if (i == varList.size() - 1) // And it's the last one…
return ERR_NONEXISTENT; // Uh oh!
} else { // Found it!
varList[i].value = newValue;
}
}
return 0;
}
fetchResult fetchVar(string varName){
fetchResult returnValue;
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name != varName){ // If it doesn't match…
if (i == varList.size() - 1){ // And it's the last one…
returnValue.good = false; // Uh oh!
returnValue.result = -1;
} else {
returnValue.good = true;
returnValue.result = varList[i].value;
}
}
}
return returnValue;
}
bool checkVar(string varName){
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name != varName){ // If it doesn't match…
if (i == varList.size() - 1) // And it's the last one…
return false; // It's not here.
}else break;
}
return true;
}
vector < var > getVarList(){
return varList;
}
string getVarList(string varDelim, string valueDelim){
stringstream final;
for (unsigned int i=0; i<varList.size()-1; i++){
final<<varList[i].name<<valueDelim<<varList[i].value<<varDelim;
// add variable name, delim 1 (probably tab), variable value, delim 2 (probably newline)
}
final<<varList.back().name<<valueDelim<<varList.back().value;
// same, but don't add a newline (or other)
return final.str();
}
vsystem.h
/*
* vsystem.h
*
* Created on: Apr 29, 2011
* Author: wjc
*/
#include <vector>
#include <string>
#include "consts.h"
using namespace std;
#ifndef VSYSTEM_H_
#define VSYSTEM_H_
struct fetchResult {
float result;
bool good;
};
struct var {
string name;
float value;
};
int addVar(string varName, float value);
int changeVar(string varName, float newValue);
fetchResult fetchVar(string varName);
bool checkVar (string varName);
vector < var > getVarList();
string getVarList(string varDelim, string valueDelim);
#endif /* VSYSTEM_H_ */
ui.h
/*
* ui.cpp
*
* Created on: Apr 26, 2011
* Author: wjc
*/
#include <iostream>
#include <vector>
#include "filedaemon.h"
#include "vsystem.h"
using namespace std;
int runUI(){
cout << " Variable Systems Test "<<endl;
cout << "~~~~~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
cout << endl;
cout<<"Enter a variable name:"<<endl;
string varname;
cin>>varname;
cout<<"Enter a value (A FLOAT!):"<<endl;
float value;
cin>>value;
cout<<"Checking to see if "<<varname<<" exists."<<endl;
bool alreadythere = checkVar(varname);
alreadythere ? cout<<"It exists!"<<endl : cout<<"It doesn't exist."<<endl;
if (alreadythere){
cout<<"Changing variable. Function returned "<<changeVar(varname, value)<<endl;
} else {
cout<<"Setting variable. Function returned "<<addVar(varname, value)<<endl;
}
cout<<"Enter a variable to check:"<<endl;
string varcheck;
cin>>varcheck;
fetchResult result = fetchVar(varcheck);
if(! result.good){
cout<<"Variable \""<<varcheck<<"\" doesn't exist!"<<endl;
} else {
cout<<"Variable \""<<varcheck<<"\" is equal to "<<result.result<<endl;
}
cout<<getVarList("\n","\t")<<endl;
string exitstr;
cin>>exitstr;
return 0;
}
main.cpp只调用runUI（）
答案 0 :(得分：0)
你在向量上循环并返回true / false的方式很奇怪，你的应用程序因checkVar()而崩溃。
我建议您将varList上搜索项目的所有循环更改为更简单易读的内容，例如：
bool checkVar(string varName)
{
// Check to see if varName exists
for (unsigned int i=0; i<varList.size(); i++)
{
if (varList[i].name == varName)
{ // If matches,
return true;
}
}
// If execution reaches here, it means it didn't found a match
return false;
}
这解决了崩溃问题。我不知道您的应用程序是否有任何其他错误，但这是我目前的输出：
Building Generator 1.0 Alpha
Variable Systems Test
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Enter a variable name:
dog
Enter a value (A FLOAT!):
2.2
Setting variable. Function returned 0
Enter a variable to check:
alpha
Variable "alpha" doesn't exist!
dog 2.2
修改
另一个问题是你的定义：ERR_NONEXISTENT和ERR_VAR_EXISTS都是1。他们应该有不同的价值观！我正在粘贴下面的相关代码：
<强> consts.h ：
#ifndef CONSTS_H_
#define CONSTS_H_
#define VERSION "1.0 Alpha"
// Variable errors
#define ERR_NONEXISTENT 0
#define ERR_VAR_EXISTS 1
// File r/w errors
#define ERR_FILE_OPEN 2
#endif /* CONSTS_H_ */
<强> vsystem.cpp ：
#include <string>
#include <vector>
#include <sstream>
#include "vsystem.h"
using namespace std;
vector <var> varList;
int addVar(string varName, float value){
// Check to see if varName already exists
bool varExists = false;
for (unsigned int i=0; i<varList.size(); i++){
if (varList[i].name == varName){
varExists = true;
return ERR_VAR_EXISTS;
}
}
// Good! The variable doesn't exist yet.
var tempVar;
tempVar.name = varName;
tempVar.value = value;
varList.push_back(tempVar);
return ERR_NONEXISTENT;
}
int changeVar(string varName, float newValue){
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name == varName)
{ // If it match, replace the value
varList[i].value = newValue;
return ERR_VAR_EXISTS;
}
}
return ERR_NONEXISTENT; // Uh oh!
}
fetchResult fetchVar(string varName){
fetchResult returnValue;
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name == varName){ // If it matches
if (i == varList.size() - 1)
{
returnValue.good = true;
returnValue.result = varList[i].value;
return returnValue;
}
}
}
returnValue.good = false; // Uh oh!
returnValue.result = -1;
return returnValue;
}
bool checkVar(string varName)
{
// Check to see if varName exists
for(unsigned int i=0; i<varList.size(); i++){
if(varList[i].name == varName)
{ // If matches, return true
return true;
}
}
// If execution reaches here, it means it didn't found a match
return false;
}
vector < var > getVarList(){
return varList;
}
string getVarList(string varDelim, string valueDelim){
stringstream final;
for (unsigned int i=0; i<varList.size()-1; i++){
final<<varList[i].name<<valueDelim<<varList[i].value<<varDelim;
// add variable name, delim 1 (probably tab), variable value, delim 2 (probably newline)
}
final<<varList.back().name<<valueDelim<<varList.back().value;
// same, but don't add a newline (or other)
return final.str();
}