Question

我是Django的新手（已使用1.11），我读了这篇文章（https://docs.djangoproject.com/fr/1.11/topics/db/models/），但我没有找到一个明确的答案：如何检索对象

举一个例子，假设我有以下模型：

#include <iostream>
#include <string>
#include <QuartzCore/QuartzCore.h>
#include <CoreServices/CoreServices.h>
#include <ImageIO/ImageIO.h>

int main(int argc, const char * argv[]) {
    std::string baseImageOutput = "/Users/bogdan/Desktop";
    std::string pathSeparator = "/";
    std::string baseImageName = "image-";
    std::string imageExtension = ".png";

    CGDisplayCount displayCount;
    CGDirectDisplayID displays[32];

    // grab the active displays
    CGGetActiveDisplayList(32, displays, &displayCount);

    // go through the list
    for (int i = 0; i < displayCount; i++) {
        std::string imagePath = baseImageOutput + pathSeparator + baseImageName + std::to_string(i) + imageExtension;
        const char *charPath = imagePath.c_str();

        CFStringRef imageOutputPath = CFStringCreateWithCString(kCFAllocatorDefault, charPath, kCFURLPOSIXPathStyle);
        // make a snapshot of the current display
        CGImageRef image = CGDisplayCreateImage(displays[i]);

        CFURLRef url = CFURLCreateWithString(kCFAllocatorDefault, imageOutputPath, NULL);

        // The following CGImageDestinationRef variable is NULL
        CGImageDestinationRef destination = CGImageDestinationCreateWithURL(url, kUTTypePNG, 1, NULL);

        if (!destination) {
            std::cout<< "The destination does not exist: " << imagePath << std::endl;
            CGImageRelease(image);
            return 1;
        }

        CGImageDestinationAddImage(destination, image, NULL);

        if (!CGImageDestinationFinalize(destination)) {
            std::cout << "Failed to write image to the path" << std::endl;;
            CFRelease(destination);
            CGImageRelease(image);
            return 1;
        }

        CFRelease(destination);
        CGImageRelease(image);
    }

    std::cout << "It Worked. Check your desktop" << std::endl;;
    return 0;
}

技能历史：

class StudentCollaborator(models.Model):
    user = models.OneToOneField(User, on_delete=models.CASCADE)
    code_postal = models.IntegerField()
    collaborative_tool = models.BooleanField(default=False)

    def get_skills(self):
        return SkillHistory.objects.filter(student=self.user, value="acquired").values_list('skill')

最后是技能课程：

class SkillHistory(models.Model):
    """
        The reason why a Skill is acquired or not,
        or not yet, when and by who/how

    """

    skill = models.ForeignKey(Skill)
    """The Skill to validate"""
    student = models.ForeignKey('users.Student')
    """The Student concerned by this Skill"""
    datetime = models.DateTimeField(auto_now_add=True)
    """The date the Skill status was created"""
    value = models.CharField(max_length=255, choices=(
        ('unknown', 'Inconnu'),
        ('acquired', 'Acquise'),
        ('not acquired', 'None Acquise'),
    ))
    """The Skill status : unknown, acquired or not acquired"""

    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    reason_object = GenericForeignKey('content_type', 'object_id')
    reason = models.CharField(max_length=255)
    """Why the Skill is validated or not"""

    by_who = models.ForeignKey(User)

    class Meta:
        ordering = ['datetime']

如何在get_skills函数中检索Skill对象（而不是ID）;谢谢？

由于

Answer 1

您无法直接获取Skill对象。但您可以通过此查询获取技能属性。

SkillHistory.objects.filter(student=self.user, value="acquired").values('skill__name', 'skill__code')

Answer 2

Skill.objects.filter(skillhistory_set__student=self.user, skillhistory_set__value="acquired")

使用相关名称过滤。

Django：从关系中检索对象

2 个答案: