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Waiting until two async blocks are executed before starting another block
...y Programming Guide
Your example could look something like this:
dispatch_group_t group = dispatch_group_create();
dispatch_group_async(group,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
// block1
NSLog(@"Block1");
[NSThread sleepForTimeInterval:5.0];
NSLog(@"Bl...
How do you write a migration to rename an ActiveRecord model and its table in Rails?
...ameOldTableToNewTable < ActiveRecord::Migration
def self.up
rename_table :old_table_name, :new_table_name
end
def self.down
rename_table :new_table_name, :old_table_name
end
end
I had to go and rename the model declaration file manually.
Edit:
In Rails 3.1 & 4, ActiveReco...
The difference between fork(), vfork(), exec() and clone()
...all program (think Java's Runtime.exec()). POSIX has standardized the posix_spawn() to replace these latter two more modern uses of vfork().
posix_spawn() does the equivalent of a fork()/execve(), and also allows some fd juggling in between. It's supposed to replace fork()/execve(), mainly for non-M...
How to resize an image with OpenCV2.0 and Python2.6
...ll resize the image to have 100 cols (width) and 50 rows (height):
resized_image = cv2.resize(image, (100, 50))
Another option is to use scipy module, by using:
small = scipy.misc.imresize(image, 0.5)
There are obviously more options you can read in the documentation of those functions (cv2.r...
64-bit version of Boost for 64-bit windows
... it is also possible to use the stagedir parametter: "bjam --stagedir=./lib_64bit address-model=64 toolset=msvc threading=multi" and "bjam --stagedir=./lib toolset=msvc threading=multi"
– Odin
Jul 11 '12 at 15:20
...
Retargeting solution from .Net 4.0 to 4.5 - how to retarget the NuGet packages?
...nning under the Package Manager Console: get-package | % { update-package $_.Id -reinstall -ProjectName $_.ProjectName -ignoreDependencies }
– Kaleb Pederson
May 6 '16 at 19:18
...
How to publish a website made by Node.js to Github Pages?
...
@Akshat_Jiwan_Sharma You are right. That's also what I was knowing, but today I saw this site on github and thought that you can actually use Node.js. I didn't observe that it was just a repository in the organization. If it was the...
Why would I ever use push_back instead of emplace_back?
C++11 vectors have the new function emplace_back . Unlike push_back , which relies on compiler optimizations to avoid copies, emplace_back uses perfect forwarding to send the arguments directly to the constructor to create an object in-place. It seems to me that emplace_back does everything p...
What's the point of map in Haskell, when there is fmap?
... the GHC.Base source code, the map function is implemented as follows
map _ [] = []
map f (x:xs) = f x : map f xs
which makes use of pattern matching to pull the head (the x) off the tail (the xs) of the list, then constructs a new list by using the : (cons) value constructor so to prepend f ...
Check if at least two out of three booleans are true
...he following on my machine (running Ubuntu on Intel Core 2 + sun java 1.6.0_15-b03 with HotSpot Server VM (14.1-b02, mixed mode)):
First and second iterations:
a&&b || b&&c || a&&c : 1740 ms
a ? b||c : b&&c : 1690 ms
a&b | b&c | c&a : 835 ms
...