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How do I extract a sub-hash from a hash?
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If you specifically want the method to return the extracted elements but h1 to remain the same:
h1 = {:a => :A, :b => :B, :c => :C, :d => :D}
h2 = h1.select {|key, value| [:b, :d, :e, :f].include?(key) } # => {:b=>:B, :d=...
When is null or undefined used in JavaScript? [duplicate]
...various scenarios:
You declare a variable with var but never set it.
var foo;
alert(foo); //undefined.
You attempt to access a property on an object you've never set.
var foo = {};
alert(foo.bar); //undefined
You attempt to access an argument that was never provided.
function myFunction (fo...
How do I get SUM function in MySQL to return '0' if no values are found?
...iddle.com/#!2/d1542/3/0
More Information:
Given three tables (one with all numbers, one with all nulls, and one with a mixture):
SQL Fiddle
MySQL 5.5.32 Schema Setup:
CREATE TABLE foo
(
id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
val INT
);
INSERT INTO foo (val) VALUES
(null),(1),(n...
Hiding textarea resize handle in Safari
...g textarea components in my application, and I control their height dynamically. As the user types, the height is increased whenever there is enough text. This works fine on IE, Firefox, and Safari.
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Step-by-step debugging with IPython
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You can use IPython's %pdb magic. Just call %pdb in IPython and when an error occurs, you're automatically dropped to ipdb. While you don't have the stepping immediately, you're in ipdb afterwards.
This makes debugging individual functions easy, as you can just lo...
`levels
...a functional language and does not like to mutate its objects. But it does allow assignment statements, using replacement functions:
levels(x) <- y
is equivalent to
x <- `levels<-`(x, y)
The trick is, this rewriting is done by <-; it is not done by levels<-. levels<- is just ...
Set TextView text from html-formatted string resource in XML
...that's not documented (I tripped over it after searching for hours, and finally found it in the bug list for the Android SDK itself). You CAN include raw HTML in strings.xml, as long as you wrap it in
<![CDATA[ ...raw html... ]]>
Example:
<string name="nice_html">
<![CDATA[
<p...
Assign variables to child template in {% include %} tag Django
... it's pretty simple:
{% include "subject_file_upload.html" with form=form foo=bar %}
The documentation for include mentions this. It also mentions that you can use only to render the template with the given variables only, without inheriting any other variables.
Thank you @Besnik
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S3 Static Website Hosting Route All Paths to Index.html
... URLs, it will not resolve to anything. What I need is the ability to take all url requests and serve up the root index.html in my S3 bucket, rather than just doing a full redirect. Then my javascript application could parse the URL and serve the proper page.
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Does name length impact performance in Redis?
I like to use verbose names in Redis, for instance set-allBooksBelongToUser:$userId .
4 Answers
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