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How to express a One-To-Many relationship in Django
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In Django, a one-to-many relationship is called ForeignKey. It only works in one direction, however, so rather than having a number attribute of class Dude you will need
class Dude(models.Model):
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class PhoneNumber(models.Model):
dude = models.ForeignKe...
转：postfix安装Q&A - 更多技术 - 清泛网 - 专注C/C++及内核技术
... SYS_MYSQL_SOCKET = /tmp/mysql.sock
QUOTE:
Q：
Can't call method "prepare" on an undefined value at /usr/local/httpd/htdocs/extman/libs/Ext/Mgr/MySQL.pm line 59.
A:
在mysql.pm里将RaiseError => 0 改为1 这个是打开mysql更多的出错提示。
QUOTE:...
Index on multiple columns in Ruby on Rails
...columns in sequence starting at the beginning. i.e. if you index on [:user_id, :article_id], you can perform a fast query on user_id or user_id AND article_id, but NOT on article_id.
Your migration add_index line should look something like this:
add_index :user_views, [:user_id, :article_id]
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How to go back to lines edited before the last one in Vim?
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@Bob - are you still alive? please can you make judgement call on correct answer. This answer has enough votes to warrant serious contention ;)
– arcseldon
Dec 22 '15 at 13:17
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String.replaceAll without RegEx
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This doesn't just replace the first? Weird they called it "replaceAll" instead of "replaceRegex".
– Magic Octopus Urn
Mar 28 '18 at 20:13
6
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C++ convert vector to vector
... if you don't specify the size beforehand, then it will be resized automatically whenever the capacity is exceeded (which copies all the elements over and over again). Okay, this is amortized linear time, but I bet that's still a lot slower than a single 0-initialization. Am I missing something abou...
TypeScript: problems with type system
...ave a problem with its type system. My html site has a canvas tag with the id "mycanvas". I'm trying to draw a rectangle on this canvas. Here's the code
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Python's json module, converts int dictionary keys to strings
... which implement a __hash__ method. (The Lua docs suggest that it automatically uses the object's ID as a hash/key even for mutable objects and relies on string interning to ensure that equivalent strings map to the same objects).
In Perl, Javascript, awk and many other languages the keys for has...
Styling an input type=“file” button
...the input will not respond to the likes of:
<input type="file" style="width:200px">
Instead, you will need to use the size attribute:
<input type="file" size="60" />
For any styling more sophisticated than that (e.g. changing the look of the browse button) you will need to look at ...
Best way to create an empty map in Java
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You'll have to use the latter sometimes when the compiler cannot automatically figure out what kind of Map is needed (this is called type inference). For example, consider a method declared like this:
public void foobar(Map<String, String> map){ ... }
When passing the empty Map direc...