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What is an optional value in Swift?
...long with Generics) are one of the most difficult Swift concepts to understand. Because of how they are written and used, it's easy to get a wrong idea of what they are. Compare the optional above to creating a normal String:
var name: String = "Bertie" // No "?" after String
From the syntax it loo...
What does %w(array) mean?
...otation to write an array of strings separated by spaces instead of commas and without quotes around them. You can find a list of ways of writing literals in zenspider's quickref.
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find() with nil when there are no records
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Yes, just do:
Challenge.find_by_id(10)
For Rails 4 and 5:
Challenge.find_by(id: 10)
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Counting inversions in an array
... find all inversion pairs such that A[i] > A[j] . I'm using merge sort and copying array A to array B and then comparing the two arrays, but I'm having a difficult time seeing how I can use this to find the number of inversions. Any hints or help would be greatly appreciated.
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Remove all the children DOM elements in div
... @Eugene: Could you say more about that?
– Tom Anderson
Aug 28 '11 at 15:39
7
@Tom: dojox.g...
git: Switch branch and ignore any changes without committing
I was working on a git branch and was ready to commit my changes, so I made a commit with a useful commit message. I then absentmindedly made minor changes to the code that are not worth keeping. I now want to change branches, but git gives me,
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How can I change or remove HTML5 form validation default error messages?
For example I have a textfield . The field is mandatory, only numbers are required and length of value must be 10. When I try to submit form with value which length is 5, the default error message appears: Please match the requested format
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Full examples of using pySerial package [closed]
...show me a full python sample code that uses pyserial , i have the package and am wondering how to send the AT commands and read them back!
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Simplest way to detect a mobile device in PHP
...Code:
<?php
$useragent=$_SERVER['HTTP_USER_AGENT'];
if(preg_match('/(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|netfront|opera m(ob|in)i|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|...
Javascript - removing undefined fields from an object [duplicate]
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A one-liner using ES6 arrow function and ternary operator:
Object.keys(obj).forEach(key => obj[key] === undefined ? delete obj[key] : {});
Or use short-circuit evaluation instead of ternary: (@Matt Langlois, thanks for the info!)
Object.keys(obj).forEach(...