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Create singleton using GCD's dispatch_once in Objective-C

...ectly acceptable and thread-safe way to create an instance of your class. It may not technically be a "singleton" (in that there can only ever be 1 of these objects), but as long as you only use the [Foo sharedFoo] method to access the object, this is good enough. ...
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What is the proper way to check for null values?

I love the null-coalescing operator because it makes it easy to assign a default value for nullable types. 10 Answers ...
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Changing route doesn't scroll to top in the new page

...ur when the route changes. In the step 11 of the tutorial http://angular.github.io/angular-phonecat/step-11/app/#/phones you can see the list of phones. If you scroll to the bottom and click on one of the latest, you can see that the scroll isn't at top, instead is kind of in the middle. ...
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How to len(generator()) [duplicate]

...e no length, they aren't collections after all. Generators are functions with a internal state (and fancy syntax). You can repeatedly call them to get a sequence of values, so you can use them in loop. But they don't contain any elements, so asking for the length of a generator is like asking for t...
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Single huge .css file vs. multiple smaller specific .css files? [closed]

.... That way you'll be able to deliver a single, minimised CSS file for the site (which will be far smaller and faster than a normal single CSS source file), while maintaining the nicest development environment, with everything neatly split into components. Sass and LESS have the added advantage of v...
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Shell equality operators (=, ==, -eq)

... It's the other way around: = and == are for string comparisons, -eq is for numeric ones. -eq is in the same family as -lt, -le, -gt, -ge, and -ne, if that helps you remember which is which. == is a bash-ism, by the way. It's...
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How to check a checkbox in capybara?

... I found the following worked for me: # Check find(:css, "#cityID[value='62']").set(true) # Uncheck find(:css, "#cityID[value='62']").set(false) share | improve this answer ...
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foreach vs someList.ForEach(){}

There are apparently many ways to iterate over a collection. Curious if there are any differences, or why you'd use one way over the other. ...
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avoid page break inside row of table

... when I convert html to PDF by wkhtmltopdf. I use page-break-inside:avoid with table- its works, but I have so many rows, then not work. If set display of tr as block or some thing else then it change the formatting of table and insert double border. Or it is possible to insert the table header o...
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How do I find an element that contains specific text in Selenium Webdriver (Python)?

I'm trying to test a complicated javascript interface with Selenium (using the Python interface, and across multiple browsers). I have a number of buttons of the form: ...