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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")
})
...
Scala: Abstract types vs generics
... Sommers (May 18, 2009)
Update (October2009): what follows below has actually been illustrated in this new article by Bill Venners:
Abstract Type Members versus Generic Type Parameters in Scala (see summary at the end)
(Here is the relevant extract of the first interview, May 2009, emphasis min...
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...
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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File Explorer in Android Studio
... files should be in:
DDMS-> File Explorer ->data -> data -> MY_PACKAGE_NAME -> shared_prefs -> YOUR_PREFERENCE_NAME.xml
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How do I merge a list of dicts into a single dict?
... this:
from functools import reduce
reduce(lambda a, b: dict(a, **b), list_of_dicts)
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How can I import a database with MySQL from terminal?
...;databasename> < <filename.sql>
Example:
mysql -u root -p wp_users < wp_users.sql
mysql -u root -pPassword123 wp_users < wp_users.sql
See also:
4.5.1.5. Executing SQL Statements from a Text File
Note: If you are on windows then you will have to cd (change directory) to y...