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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 to get a pixel's x,y coordinate color from an image?
...ur PNG. The following creates an off-screen canvas that is the same width and height as your image and has the image drawn on it.
var img = document.getElementById('my-image');
var canvas = document.createElement('canvas');
canvas.width = img.width;
canvas.height = img.height;
canvas.getContext('2...
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 ...
windows service vs scheduled task
What are the cons and pros of windows services vs scheduled tasks for running a program repeatedly (e.g. every two minutes)?
...
Remove the bottom divider of an android ListView
...
Just add
android:footerDividersEnabled="false"
to your ListView description
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Bootstrap carousel multiple frames at once
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Updated 2019...
Bootstrap 4
The carousel has changed in 4.x, and the multi-slide animation transitions can be overridden like this...
.carousel-inner .carousel-item-right.active,
.carousel-inner .carousel-item-next {
transform: translateX(33.33%);
}
.carousel-inner .carousel-item-l...
When should the xlsm or xlsb formats be used?
... (in particular, .xlsx , .xlsm , .xlsb ). I've got no problem to understand the use and purpose of .xlsx format but I am still wondering whether we should use a .xlsm or a .xlsb format when creating a file containing some VBA.
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Declaring variables inside loops, good practice or bad practice?
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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 ...
How can I reverse the order of lines in a file?
...
BSD tail:
tail -r myfile.txt
Reference: FreeBSD, NetBSD, OpenBSD and OS X manual pages.
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Unicode, UTF, ASCII, ANSI format differences
...fference between the Unicode , UTF8 , UTF7 , UTF16 , UTF32 , ASCII , and ANSI encodings?
2 Answers
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