主要课程：

std::vector<float> * dvertex=NULL;

track.calculate(irrelevant stuff,dvertex)

二级程序(跟踪,计算)

track::caclulate(irrelevant stuff,vector<float> * dvertex)
{
...
vector<float> pos;
... pos filled after some calculations
if(! (dvertex==NULL))
{
  dvertex = &pos1;
}

回到小学,除非我弄乱了上面的东西,这里有一些我尝试过的东西

1

(*dvertex).at(0)
float z = (*dvertex).at(0)

2

(*dvertex)[0]

和一堆简单的东西没有编译.由于我不确定如何在主程序中从该向量中获取特定值,所以我很困惑.我甚至认为它可能是if(！(dvertex == NULL))位,因此我将其更改为if(dvertex == NULL)但仍然没有快乐.任何帮助将不胜感激.

*编辑/更新*非常感谢大家的帮助,但我担心我仍然做错了.

所以按照我刚刚传递参考的建议：我这样做了：

主

std::vector<float> dvertex;
track.calculate( foo,&dvertex);

二级保持不变(有！空检查)

主

std::cout<<dvertex[0]<<std:endl;

(以及实际使用数据的其他尝试)

非常感谢您对我仍然做得不正确的想法.一切都编译好,当程序达到使用dvertex数据的程度时,程序就会冻结.

编辑：最终修复

在我需要的二级课程中

*dvertex = pos1;

代替

dvertex = &pos1;

void f(std::vector<int>* v)
{
    if( v != 0 ) {
        int n = (*v)[0];     // ok
        int m = (*v).at(0);  // ok
        int o = v->at(0);    // ok
    }
}

但别介意.如果必须更改向量,请使用引用;如果不能,则使用const引用.很少需要通过指针来获取容器.

另外,我建议您检查针对0的指针,而不是NULL,因为有时根据C编译器将NULL定义为(void *)0.但有些人可能会在这里反驳.

Game_info.h

#import <UIKit/UIKit.h>

@interface Game_Info : UIViewController {
    IBOutlet UITextField *groupName;
    IBOutlet UISegmentedControl *gameType;

}

@property (nonatomic,retain) IBOutlet UITextField *groupName;


- (IBAction) GameTypePicker;
- (IBAction) KeyboardHide;
- (IBAction) BackBTN;
- (IBAction) NextBTN;

@end

Game_Info.m

#import "I_Dare_YouViewController.h"
#import "Game_Info.h"
#import "Game_TDoR.h"


    @implementation Game_Info
    @synthesize groupName;


// Next Button
-(IBAction) NextBTN{
    if ([groupName.text length] == 0) {
        // Alert
        UIAlertView *alert = [[UIAlertView alloc] 
                              initWithTitle:@"Group Name" 
                              message:@"Please enter a group name" 
                              delegate:self 
                              cancelButtonTitle:@"OK" 
                              otherButtonTitles:nil
                              ];
        [alert show];
        [alert release];
    }else if([groupName.text length] < 3){
        // Alert
        UIAlertView *alert = [[UIAlertView alloc] 
                              initWithTitle:@"Group Name" 
                              message:@"Please enter a name longer than 3 characters" 
                              delegate:self 
                              cancelButtonTitle:@"OK" 
                              otherButtonTitles:nil
                              ];
        [alert show];
        [alert release];
    }else{
        Game_TDoR *screen = [[Game_TDoR alloc] initWithNibName:nil bundle:nil];
        screen.modalTransitionStyle = UIModalTransitionStyleCrossdissolve;
        [self presentModalViewController:screen animated:YES];
        [screen release];

        Game_TDoR *screen1 = [[Game_TDoR alloc] initWithNibName:nil bundle:nil];
        NSLog(@"Game_Info: %@",self.groupName.text);
        screen1.groupNameText = self.groupName.text; 
        [self presentModalViewController:screen1 animated:YES];
        [screen1 release];

    }
}

然后在另一个视图/ .h / .m文件中,我试图进入’groupName’属性.

Game_TDoR.m

#import "I_Dare_YouViewController.h"
#import "Game_Info.h"
#import "Game_TDoR.h"
@implementation Game_TDoR
@synthesize groupNameText,Testlbl;


- (void)viewDidLoad
{
    NSLog(@"Game_TDoR: %@",self.groupNameText);
    Nsstring *msg = [[Nsstring alloc] initWithFormat:@"Hello,%@",[self.groupNameText capitalizedString]];
    [Testlbl setText:msg];
    [msg release];

    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

所以我想要做的是在第一个视图页面(Game_info)上有一个输入文本框,我试图将其传递给另一个视图页面上的标签(Game_TDoR)

这是NSLog中出现的内容(注意第二页(Game_TDoR)在日志中首先出现.

2011-07-17 00:25:34.765 I Dare You[3941:207] Game_TDoR: (null)
2011-07-17 00:25:34.774 I Dare You[3941:207] Game_Info: Name

问题解决了：

在下一个按钮我需要在移动页面之前添加变量(而不是相反的方式 – 愚蠢的noobish事情要做…)

Game_TDoR *screen1 = [[Game_TDoR alloc] initWithNibName:nil bundle:nil];
        NSLog(@"Game_Info: %@",self.groupName.text);
        screen1.groupNameText = self.groupName.text; 
        [self presentModalViewController:screen1 animated:YES];
        [screen1 release];

        Game_TDoR *screen = [[Game_TDoR alloc] initWithNibName:nil bundle:nil];
        screen.modalTransitionStyle = UIModalTransitionStyleCrossdissolve;
        [self presentModalViewController:screen animated:YES];
        [screen release];

1)在Game_TDoR @interface块中声明Nsstring属性：

@property (nonatomic,copy) Nsstring *groupNameText;

(记得在实现块中合成或实现访问器方法)

2)在NextBTN操作中,初始化Game_TDoR实例后,设置属性：

Game_TDoR *screen = [[Game_TDoR alloc] init...];
screen.groupNameText = self.groupName.text;

所以在代码中它将是这样的：

var response;

$.post(url,function(resp){
   response = resp;
})

function doSomething() {
  // do something with the response here
}

VS

$.post(url,function(resp){
   doSomething(resp);
})

function doSomething(resp) {
  // do something with the resp here
}

假设resp是一个大对象或字符串,它可以在多个函数之间传递.

这意味着将它们传递给函数并不昂贵,因为没有复制.传递给函数的所有内容只是指向原始对象的指针,这是有效的.

您还需要意识到您的第一个方案甚至无法正常工作：

var response;

$.post(url,function(resp){
   response = resp;
})

function doSomething() {
  // do something with the response here
}

因为时间的关系,你不知道何时调用doSomething(). $.post(),因为你显示它是异步的,因此你不知道它何时实际完成.代码中的resp值必须在完成函数中使用.您必须在完成函数中使用它,或者从完成函数调用一些东西并将resp传递给它(就像您的第二个示例).只有这样,您才能获得有关数据可用时的正确时间.