我如何循环通过stl :: List并存储其中一个对象的值,以便稍后在函数中使用？
Particle *closestParticle;
for(list<Particle>::iterator p1 = mParticles.begin(); p1 != mParticles.end(); ++p1 )
{
// Extra stuff removed
closestParticle = p1; // fails to compile (edit from comments)
}
当我尝试保存CoreData模型的上下文时,收到错误
Unresolved error Error Domain=NSCocoaErrorDomain Code=1560 "The operation couldn’t be completed. (Cocoa error 1560.)" UserInfo=0x76924b0 {NSDetailedErrors=(
"Error Domain=NSCocoaErrorDomain Code=1570 "
The operation couldn\U2019t be completed. (Cocoa error 1570.)"
UserInfo=0x768c410 {NSValidationErrorObject=<Posts: 0x7177990> (entity: Posts; id: 0x7177010 <x-coredata:///Posts/tEF7138E6-A968-45B7-95CF-116C2AA93D605> ; data: {\n "
business_entity"
= nil;\n "
created_at"
= "
2012-01-21 03:31:30 +0000"
;\n "
own_description"
= "
Roasted this morning- Panama Duncan Estate: A rose fragrance debuts flavors of pear, coconut and marshmallow with caramel throughout the cup."
;\n postsID = 4;\n …
我在我的应用程序中遇到问题,CoreData在模拟器中工作正常 - 但不在设备上.
我收到了
2010-09-30 12:45:07.500 CoreDataTutorial_iOS[130:307] Unresolved error Error Domain=NSCocoaErrorDomain Code=513 "The operation couldn’t be completed. (Cocoa error 513.)" UserInfo=0x1412a0 {NSUnderlyingException=Error validating url for store}, {
NSUnderlyingException = "Error validating url for store";
我在这个函数中调用PersistentStoreCoordinator(抛出上面的错误):
-(NSPersistentStoreCoordinator*)persistentStoreCoordinator
{
if(persistentStoreCoordinator_ != nil)
return persistentStoreCoordinator_;
NSURL *aStoreURL = [NSURL fileURLWithPath: [[self applicationDocumentsDirectory] stringByAppendingFormat:@"corebase.sqlite"]];
NSError *anError = nil;
persistentStoreCoordinator_ = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
if(![persistentStoreCoordinator_ addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:aStoreURL options:nil error:&anError])
{
NSLog(@"Unresolved error %@, %@", anError, [anError userInfo]);
abort();
}
return persistentStoreCoordinator;
}
我在"objc_exception_throw"上设置了一个断点,看看aStoreURL是什么,它是:file://localhost/var/mobile/Applications/BE9A2982-BDC3-405D-A201-FB78E9E0790B/Documentscorebase.sqlite …
我不确定这是做什么的.dateFormatter第一次只能设置吗？
static NSDateFormatter *dateFormatter = nil;
if (dateFormatter == nil) {
dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
[dateFormatter setDateStyle:NSDateFormatterMediumStyle];
}
通常我会读到这意味着,设置为零,然后检查它是否为零,但如果我在条件内的NSLog,它只被调用一次？
额外的点,如果你可以更深入地解释静态,我知道它创建一个全局变量(？),但这就是它.
所以在C++中,如果我创建一个使用的对象,new我应该总是使用delete
例如解除分配它
Segment::Segment(float length)
{
segmentLength = length;
angle = 0.0f;
x = Rand::randFloat(1.0f, 1.5f);
y = Rand::randFloat(1.0f, 1.5f);
vx = Rand::randFloat(0.0f, 1.0f);
vy = Rand::randFloat(0.0f, 1.0f);
prevX = Rand::randFloat(0.0f, 1.0f);
prevX = Rand::randFloat(0.0f, 1.0f);
};
并且我可以说我在另一个类中使用它,例如
this._segmentObject = Segment(2.0f);
this._segmentPointer = new Segment(2.0f);
在该类的析构函数中,我知道我应该调用deletethis._segmentPointer,但是如何确保为另一个释放内存呢？
这可能是一个简单的问题,但这是我的用例:
需要在旧分支中看到一些东西,运行
git log -10
它告诉我,我不在任何分支,所以我跑
git checkout master
但是,在我检查了之前的提交后,我似乎无法回到当前的提交.我收到了这条消息
:$ git checkout master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 7 commits.
:$ git pull
Already up-to-date.
我如何从那回到当前版本的主分支？