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Ruby on Rails: How can I revert a migration with rake db:migrate?
...to revert.
eg. if you want to revert a migration with file name 3846656238_create_users.rb
rake db:migrate:down VERSION=3846656238
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In Swift how to call method with parameters on GCD main thread?
...() + 0.1) {
// your code here
}
Older versions of Swift used:
dispatch_async(dispatch_get_main_queue(), {
let delegateObj = UIApplication.sharedApplication().delegate as YourAppDelegateClass
delegateObj.addUIImage("yourstring")
})
...
mmap() vs. reading blocks
I'm working on a program that will be processing files that could potentially be 100GB or more in size. The files contain sets of variable length records. I've got a first implementation up and running and am now looking towards improving performance, particularly at doing I/O more efficiently since...
Add days to JavaScript Date
...w Date();
console.log(date.addDays(5));
This takes care of automatically incrementing the month if necessary. For example:
8/31 + 1 day will become 9/1.
The problem with using setDate directly is that it's a mutator and that sort of thing is best avoided. ECMA saw fit to treat Date as a mutab...
Best way to pretty print a hash
...
require 'pp'
pp my_hash
Use pp if you need a built-in solution and just want reasonable line breaks.
Use awesome_print if you can install a gem. (Depending on your users, you may wish to use the index:false option to turn off displaying arr...
How to dismiss keyboard iOS programmatically when pressing return
...s delegate to current viewcontroller and then:
func textFieldShouldReturn(_ textField: UITextField) -> Bool {
textField.resignFirstResponder()
return true
}
Objective-C:
[self.view endEditing:YES];
or
Set text field's delegate to current viewcontroller and then:
- (BOOL)textFie...
overlay opaque div over youtube iframe
...text/html" width="520" height="330" src="http://www.youtube.com/embed/NWHfY_lvKIQ?wmode=opaque" frameborder="0"></iframe>
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How to generate .json file with PHP?
...rom Posts limit 20";
$response = array();
$posts = array();
$result=mysql_query($sql);
while($row=mysql_fetch_array($result)) {
$title=$row['title'];
$url=$row['url'];
$posts[] = array('title'=> $title, 'url'=> $url);
}
$response['posts'] = $posts;
$fp = fopen('results.json', 'w...
Convert string to a variable name
...an.r-project.org/doc/FAQ/R-FAQ.html#How-can-I-turn-a-string-into-a-variable_003f
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What is an optional value in Swift?
...g and writing code more fluent. Unfortunately this obscures the way it actually works. I'll go through some of the tricks later.
Note: I'll be talking about optional variables a lot, but it's fine to create optional constants too. I mark all variables with their type to make it easier to understand ...