Question

我试图理解这些东西是如何工作的：NSEntityDescription，NSAttributeDescription，attributeType。

我认为这几行代码有效，因为我得到了我对X值的期望。有人可以告诉我应该如何修改循环的内部部分，即行：X ++; 为了获得实体中属性的名称和类型：“myentity”？

//::::::::::::::::::::::::::: EXPERIMENT    
MeDaSyAGAppDelegate *TheAppDelegate=[[UIApplication sharedApplication] delegate];
NSManagedObjectContext *TheContext=[TheAppDelegate managedObjectContext];
NSEntityDescription *TheEntityDesc;
TheEntityDesc=[NSEntityDescription entityForName:@"myentity" inManagedObjectContext:TheContext];
int X=0;
NSDictionary *attribs=[TheEntityDesc attributesByName];
for (NSAttributeDescription *eachA in [attribs allValues]) {
    X++;
}       
[self showMessageBox:[NSString stringWithFormat:@"X = %d.",X]];
//::::::::::::::::::::::::::: EXPERIMENT

Answer 1

首先：格式化代码。见下文。

第二：尝试这样做：

NSLog(@"%@",eachA.name);//The name
NSLog(@"%d",[eachA attributeType])//The type, this is an integer
NSLog(@"%@",[eachA attributeValueClassName]);//Class name receiver

请参阅：NSAttributeDescription Class Docs

格式化：这看起来更好。（属性从小写开始并使用空格）

//::::::::::::::::::::::::::: EXPERIMENT    
MeDaSyAGAppDelegate *theAppDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *theContext = [TheAppDelegate managedObjectContext];
NSEntityDescription *theEntityDesc = [NSEntityDescription entityForName:@"myentity" inManagedObjectContext:TheContext];
int X = 0;
NSDictionary *attribs = [theEntityDesc attributesByName];
for (NSAttributeDescription *eachA in [attribs allValues]) {
    X++;
}       
[self showMessageBox:[NSString stringWithFormat:@"X = %d.", X]];
//::::::::::::::::::::::::::: EXPERIMENT

NSEntityDescription和NSAttributeDescription如何工作？

1 个答案: