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How can I rename a database column in a Ruby on Rails migration?
...mething else or do nothing
end
end
For Rails 3.1 use:
While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".
See "Active Record...
How do you check whether a number is divisible by another number (Python)?
...le of 5. The way I thought I'd do this would be to divide the number by 3, and if the result is an integer then it would be a multiple of 3. Same with 5.
...
How to create a release signed apk file using Gradle?
...KEY_ALIAS=*****
RELEASE_KEY_PASSWORD=*****
Modify your app/build.gradle, and add this inside the android { code block:
...
signingConfigs {
release {
storeFile file(RELEASE_STORE_FILE)
storePassword RELEASE_STORE_PASSWORD
keyAlias RELEASE_KEY_ALIAS
keyPassword ...
Disable/enable an input with jQuery?
...).prop('disabled', true);
$("input").prop('disabled', false);
jQuery 1.5 and below
The .prop() function doesn't exist, but .attr() does similar:
Set the disabled attribute.
$("input").attr('disabled','disabled');
To enable again, the proper method is to use .removeAttr()
$("input").removeAtt...
Declaring variables inside loops, good practice or bad practice?
...
The compiler knows that the variable scope is limited to inside the loop, and therefore will issue a proper error message if the variable is by mistake referenced elsewhere.
Last but not least, some dedicated optimization can be performed more efficiently by the compiler (most importantly register ...
Why is transposing a matrix of 512x512 much slower than transposing a matrix of 513x513?
...
The explanation comes from Agner Fog in Optimizing software in C++ and it reduces to how data is accessed and stored in the cache.
For terms and detailed info, see the wiki entry on caching, I'm gonna narrow it down here.
A cache is organized in sets and lines. At a time, only one set is u...
Visual Studio debugging/loading very slow
...") my ASP.NET MVC sites. Not always: at first, the projects will load nice and fast, but once they load slow, they'll always load slow after that. I could be waiting 1-2 minutes or more.
...
How to take column-slices of dataframe in pandas
...achine learning data from a CSV file. The first 2 columns are observations and the remaining columns are features.
10 Answe...
Is there any significant difference between using if/else and switch-case in C#?
... (unlike many other languages) also allows to switch on string constants - and this works a bit differently. It's obviously not practical to build jump tables for strings of arbitrary lengths, so most often such switch will be compiled into stack of IFs.
But if number of conditions is big enough t...
Replace spaces with dashes and make all letters lower-case
...
Just use the String replace and toLowerCase methods, for example:
var str = "Sonic Free Games";
str = str.replace(/\s+/g, '-').toLowerCase();
console.log(str); // "sonic-free-games"
Notice the g flag on the RegExp, it will make the replacement global...