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How to define two fields “unique” as couple
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There is a simple solution for you called unique_together which does exactly what you want.
For example:
class MyModel(models.Model):
field1 = models.CharField(max_length=50)
field2 = models.CharField(max_length=50)
class Meta:
unique_together = ('field1', 'fi...
What is “Orthogonality”?
...gn, operations do not have side effects; each action (whether it's an API call, a macro invocation, or a language operation) changes just one thing without affecting others. There is one and only one way to change each property of whatever system you are controlling.
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What characters are forbidden in Windows and Linux directory names?
...ot create a folder named A if one named a already exists. Worse, seemingly-allowed names like PRN and CON, and many others, are reserved and not allowed. Windows also has several length restrictions; a filename valid in one folder may become invalid if moved to another folder. The rules for
naming f...
What is the difference between a thread and a fiber?
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In the most simple terms, threads are generally considered to be preemptive (although this may not always be true, depending on the operating system) while fibers are considered to be light-weight, cooperative threads. Both are separate execution paths for your applic...
Rails 4 - passing variable to partial
...buyer } %>
<%= render "account", account: @buyer %>
# @account.to_partial_path returns 'accounts/account', so it can be used to replace:
# <%= render partial: "accounts/account", locals: { account: @account} %>
<%= render @account %>
# @posts is an array of Post instances, so ...
What is the difference between gravity and layout_gravity in Android?
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Basically, everything with layout_ defines something that effects the elements outside.
– Triang3l
Jun 28 '13 at 10:26
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Why can't variables be declared in a switch statement?
...lity and consistency in the code. In the old days, you might have automatically got an "extra" stack frame, but now that should not be the case for any decent optimizing compiler.
– Tall Jeff
Sep 18 '08 at 14:37
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How to sort a Ruby Hash by number value?
...ea.com" => 745, "siteb.com" => 9, "sitec.com" => 10 }
metrics.sort_by {|_key, value| value}
# ==> [["siteb.com", 9], ["sitec.com", 10], ["sitea.com", 745]]
If you need a hash as a result, you can use to_h (in Ruby 2.0+)
metrics.sort_by {|_key, value| value}.to_h
# ==> {"siteb.c...
Sort a single String in Java
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toCharArray followed by Arrays.sort followed by a String constructor call:
import java.util.Arrays;
public class Test
{
public static void main(String[] args)
{
String original = "edcba";
char[] chars = original.toCharArray();
Arrays.sort(chars);
String...
Android: create a popup that has multiple selection options
... Toast.makeText(TopicDetails.this, "you nailed it", Toast.LENGTH_SHORT).show();
} else if ("Medium".equals(fonts[which])) {
Toast.makeText(TopicDetails.this, "you cracked it", Toast.LENGTH_SHORT).show();
} else if ("Large".equals(fonts[which])) {
...