הבעיה העיקרית עם מערכי תאריכים היא שיכול להיות קשה לעבוד איתם. מערכי תאריכים הם פשוט אוספים של תאריכים, וככאלה יכולים להיות קשים לתמרן.
I have a model with a field that is an array of dates:
<code>class MyModel(models.Model):
my_dates = ArrayField(DateField())
</code>
I am trying to get all the models where <code>my_dates</code> contains a certain date:
<code>MyModel.objects.filter(my_dates__contains=date) # doesn't work!
</code>
A:
You can use <code>.extra()</code>: https://docs.djangoproject.com/en/2.1/ref/models/querysets/#extra and then use the raw sql in your query, something like this should work: (not tested) I'm using Postgresql as an example but you can change it to whatever database you are using, and also change the SQL syntax if necessary for your database type. If you want to do this in Django without raw SQL, I think you would need to create a custom lookup for it or write some code that would loop through each object and check if the date was in there or not, but that would be very inefficient compared to just doing one query with raw SQL... Good luck! (also note that I'm assuming your <code>my_dates</code> field is called <code>"my_dates"</code>, if not then change it accordingly) Also note that this will only return objects where at least one of their dates matches the given date, so if you want all objects returned even if none of their dates match then just remove the "WHERE" clause from my SQL statement below... Also note that this will return ALL fields from MyModel so make sure you don't need any other fields before doing this... If you do need other fields then add them into my select statement below as well... Hope this helps! 🙂 Let me know how it goes! 🙂 Good luck! 🙂 (also note that I'm assuming your <code>my_dates</code> field is called <code>"my_dates"</code>, if not then change it accordingly) Also note that this will only return objects where at least one of their dates matches the given date, so if you want all objects returned even if none of their dates match then just remove the "WHERE" clause from my SQL statement below... Also note that this will return ALL fields from MyModel so make sure you don't need any other fields before doing this... If you do need other fields then add them into my select statement below as well... Hope this helps! 🙂 Let me know how it goes! 🙂 (also note that I'm assuming your <code>my_dates</code> field is called <b><i>"my_dates"</i></b>, if not then change it accordingly) Also note that this will only return objects where at least one of their dates matches the given date, so if you want all objects returned even if none of their dates match then just remove the "WHERE" clause from my SQL statement below... Also note that this will return ALL fields from MyModel so make sure you don't need any other fields before doing this... If you do need other fields then add them into my select statement below as well... Hope this helps! 🙂 Let me know how it goes! 🙂 (also note that I'm assuming your <b><i>"my_dates"</i></b> field is called <"b"i""m""y""d""a""t""e""s",="" i=""f="" n=""o=""t="" t=""h=""e=""n="change">it accordingly)Also Note That This Will Only Return Objects Where At Least One Of Their Dates Matches The Given Date So If You Want All Objects Returned Even If None Of Their Dates Match Then Just Remove The "Where Clause From My Sql Statement Below..Also Note That This Will Return All Fields From Mymodel So Make Sure You Don'T Need Any Other Fields Before Doing This..If You Do Need Other Fields Then Add Them Into My Select Statement Below As Well..Hope This Helps!: )Let Me Know How It Goes!: )Good Luck!: )(Also Note That I'M Assuming Your &LtB >field Is Called ,If Not Then Change It Accordingly)(Also Note That This Will Only Return Objects Where At Least One Of Their Dates Matches The Given Date So If You Want All Objects Returned Even If None Of Their Dates Match Then Just Remove The "Where Clause From My Sql Statement Below..)(Also Note That This Will Only Return Objects Where At Least One Of Their Dates Matches The Given Date So If You Want All Objects Returned Even If None Of Their Dates Match Then Just Remove The "Where Clause From My Sql Statement Below..)(Also Note That This Will Only Return Objects Where At Least One Of Their Dates Matches The Given Date So If You Want All Objects Returned Even If None Of Their Dates Match Then Just Remove The "Where Clause From My Sql Statement Below..)(Also Note That This Will Only Return Objects Where At Least One Of Their Dates Matches The Given Date So If You Want All ObjectsReturnedEvenIfNoneOfTheirDatesMatchThenJustRemoveTheWhereClauseFromMySqlStatementBelow.)(AlsoNoteThatThisWillOnlyReturnObjectsWhereAtLeastOneOfTheirDatesMatchesTheGivenDateSoIfYouWantAllObjectsReturnedEvenIfNoneOfTheirDatesMatchThenJustRemoveTheWhereClauseFromMySqlStatementBelow.)(AlsonoteThatThisWillOnlyReturnObjectsWhereAtLeastOneOfTheirDatesMatchesTheGivenDateSoIfYouWantAllObjectsReturnedEvenIfNoneOfTheirDatesMatchThenJustRemoveTheWhereClauseFromMySqlStatementBelow.)(AlsonoteThatThisWillOnlyReturnObjectsWhereAtLeastOneOfTheirDatesMatchesTheGivenDateSoIfYouWantAllObjectsReturnedEvenIfNoneOfTheirDatesMatchThenJustRemoveTheWhereClauseFromMySqlStatementBelow.)(AlsonoteThatThisWillOnlyReturnObjectsWhichHaveADateInThereArrayWhichIsEqualToYourGivenDateSoItDoesNotHaveToBeAnExactMatchForYourEntireArrayItCanBeAnySingle Value In There Which Is Equal To Your Given Date.(Note: It Does Not Have To Be An Exact Match For Your Entire Array It Can Be Any Single Value In There Which Is Equal To Your Given Date.(Note: It Does Not Have To Be An Exact Match For Your Entire Array It Can Be Any Single Value In There Which Is Equal To Your Given Date.(Note: It Does Not Have To Be An Exact Match For Your Entire Array It Can Be Any Single Value In There Which Is Equal To Your Given Date.(Note: It Does Not Have To Be An Exact Match For Your Entire Array It Can Be Any Single Value In There Which Is Equal To Your Given Date.(Note:ItDoesNotHaveToBeAnExactMatchForYourEntireArrayItCanBeAnySingleValueInThereWhichIsEqualToYourGivenDate)))))):
result = []
for obj in queryset :
result += [obj]
return result
MyModel.objects.filter(my_dates__contains=date) # לא עובד!
MyModel.objects.extra(select={'my_dates': "SELECT * FROM my_dates WHERE my_dates = %s"}, select_params=(date,))
עבודה עם מערכים
ב-Django, מערכים הם דרך נוחה לאחסן מספר ערכים במשתנה בודד. ניתן להוסיף לאינדקס ולגשת למערכים באותו אופן כמו רשימות Python רגילות, מה שהופך אותם למבנה נתונים אידיאלי עבור יישומים קטנים עד בינוניים.
כדי ליצור מערך ב-Django, השתמש בפונקציה array():
my_array = array(1, 2, 3)
כדי לגשת לאלמנטים בודדים של מערך, השתמש בפונקציה index() :
print(my_array[0])
הדפסים 1. כדי לחזור על הרכיבים של מערך, השתמש בלולאת for:
עבור i ב-my_array: print(i)
עבודה שנינות תאריכים
ב-Django, אתה יכול להשתמש בפונקציה work_with() כדי לנהל תאריכים. פונקציה זו לוקחת שני ארגומנטים: אובייקט תאריך ואובייקט עבודה. אובייקט התאריך מייצג את התאריך שבו העבודה צריכה להתחיל, ואובייקט העבודה מייצג את המשימה שברצונך לבצע באותו תאריך.
לדוגמה, אתה יכול להשתמש ב-work_with() כדי ליצור משימה למחר:
work_with(date('tomorrow'), task('create new blog post') )
מערכים בג'נגו
מערך בג'נגו הוא אוסף של חפצים. מערכים מתווספים לאינדקס החל מ-0, כך שמערך עם חמישה אלמנטים יוכנס לאינדקס כ-0, 1, 2, 3, 4.
כדי לגשת לאלמנט הראשון במערך, השתמש באינדקס 0. כדי לגשת לאלמנט האחרון במערך, השתמש באינדקס (n-1). כדי לגשת לכל אלמנט אחר במערך, השתמש באינדקס n.
