Django：檢查哪個相關對象存在

Question

我有兩個不同的模型，引用django User，即Recruiter和Userprofile。

我有一個函數接收User對象作爲參數。我需要檢查哪些相關對象存在並採取相應的措施。我正在使用嵌套try-catch來做這件事：

def some_function(user, ....): 
    ... 
    try: 
     profile = user.userprofile 
     profile.profile_pic.save('{0}_social.jpg'.format(user.username)) 
     profile.save() 
    except: 
     try: 
      recruiter = user.recruiter 
      recruiter.cover_pic.save('{0}_social.jpg'.format(user.username)) 
      recruiter.save() 
     except: 
      pass 

有沒有更好的/更優雅的做法呢？

編輯：考慮到型號如下

class Recruiter(models.Model): 
    user = models.OneToOneField(User, unique=True, related_name='recruiter') 
    ... 

class UserProfile(models.Model): 
    user = models.OneToOneField(User, unique=True, related_name='userprofile') 
    ... 

Answer 1

可以使用.exists（）查詢集API，像這樣（假設user是用戶模型的實例，都USERPROFILE和招聘鍵與現場也被命名user），該模型：

def some_function(user, ...): 
    if Userprofile.objects.filter(user=user).exists() 
     profile = user.userprofile 
     profile.profile_pic.save('{0}_social.jpg'.format(user.username)) 
     profile.save() 
    elif Recruiter.objects.filter(user=user).exists() 
     recruiter = user.recruiter 
     recruiter.cover_pic.save('{0}_social.jpg'.format(user.username)) 
     recruiter.save() 
    else: 
     # User has neither Userprofile nor Recruiter associated with it! 
     # Do something here to handle that case, or just get rid of the else 

注意，.exists()通話將首先做一個查詢，看是否存在對象，以及訪問該對象的行（例如，user.userprofile）將運行另一個查詢以實際訪問該對象。稍微優化的方式雖然可能不太可讀，但可能不太可讀：

def some_function(user, ...): 
    userprofiles = Userprofile.objects.filter(user=user) 
    recruiters = Recruiter.objects.filter(user=user) 
    if len(userprofiles): 
     profile = userprofiles[0] 
     profile.profile_pic.save('{0}_social.jpg'.format(user.username)) 
     profile.save() 
    elif len(recruiters): 
     recruiter = recruiters[0] 
     recruiter.cover_pic.save('{0}_social.jpg'.format(user.username)) 
     recruiter.save() 
    else: 
     # User has neither Userprofile nor Recruiter associated with it! 
     # Do something here to handle that case, or just get rid of the else