鉴于以下守则:
public class Practice1 {
public enum Dogs {collie, harrier};
public static void main(String[] args) {
Dogs myDog = Dogs.collie;
switch (myDog) {
case collie:
System.out.println("collie ");
case harrier:
import java.util.List;
import java.util.ArrayList;
interface Canine {}
class Dog implements Canine {}
public class Collie extends Dog {
public static void main(String[] args){
List<Dog> d = new ArrayList<Dog>();
List<Collie> c = new ArrayList<Collie>();
class Collie
def speak
puts dog_generic
end
end
class Greyhound
def speak
puts dog_generic
end
end
class Labrador
def speak
puts dog_generic
end
end
dog_generic = "Woof"
chep = Collie.new
wrex = Collie.new
speedy = Greyhound.new
faithful
我正在使用MYSQL,并试图在MYSQL的能力范围内工作,以达到排序的目的。
我的问题是:
SELECT petz.s_name,
petz.breed,
a.num,
sum(a.rank) AS rank
FROM wins_conf a
JOIN
(SELECT DISTINCT rank
FROM wins_conf
ORDER BY rank DESC LIMIT 10) b ON a.rank = b.rank
JOIN petz ON a.num=petz.num
GROUP BY petz.num
ORDER B
我有一个具有顶级抽象类的域对象层次结构。在GORM中,它们可以这样定义:
abstract class Dog {
...
}
class Collie extends Dog {
...
}
现在,我想对传递给Dog ID的控制器进行单元测试,如下所示:
//in the unit test
new Collie(id:1).save(validate:false)
params.id = 1
controller.show()
和
//in the tested controller
def dog = Dog.get(params.id)
这适用于真实的GORM,不幸的是,测试GORM
我有三栏,列有不同品种的狗(名单要广泛得多):
Border Collie Beagle German Shepard
Australian Sheepdog Husky Australian Sheepdog
我希望结果只是一栏中的品种列表(在一个新的表格中),没有重复:
Border Collie
Australian Sheepdog
Beagle
Husky
German Shepard
我尝试过=UNIQUE(DogBreeds_),但它仍然在三列中给出了它们。DogBreeds_是所有品种的三列的宏。
谢谢你的帮助
我有以下数据
group = c("cat", "dog", "horse")
value = c("1", "2", "3")
list = c("siamese,burmese,balinese","corgi,sheltie,collie","arabian,friesian,andalusian" )
df = data.frame(group, value, list)
df
group value
我正在读这个,我试过这个例子。我注意到,当我将YoungDogs()和HerdingDogs()方法体转换为LINQ表达式时,yield return被替换为return,但是方法的行为保持不变。
为什么将方法更改为LINQ表达式会改变数据返回方式的行为?
这是本文中概述的原始示例:
public static IEnumerable<Dog> YoungDogs(this IEnumerable<Dog> dogs)
{
foreach (Dog d in dogs)
if (d.Age < 10)
我试图为用户提供在SomeModel中存储任意数量或种类的ExtraParameters列表的可能性(可以是IntegerField、BooleanField之类的小东西,也可以是TextField这样的大列表)。
我尝试实现ExtraParameter 抽象模型类,这将使ForeignKey保持到SomeModel,并且它的子类只有一个参数,例如:
class ExtraParameter(models.Model):
somemodel = models.ForeignKey(SomeModel, ...)
class Meta:
abstract = T
使用PostgreSQL,我希望能够在HStore字段中找到与给定查询匹配的所有键值对。因此,例如,给定如下表:
Name Parentage (Hstore)
_____ ___________________
Rover Mother => Yellow Lab, Father => Black Lab
Fido Mother => Black Lab, Father => Rottweiler
Rex Mother => Labrador Retriever, Father => Sp