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Factory pattern in C#: How to ensure an object instance can only be created by a factory class?
...some check before creating an object, probably in its constructor. This is all okay until I decide I want to make this check be a part of the business logic. So, how can I arrange for a business object to be creatable only through some method in my business logic class but never directly? The first ...
Can functions be passed as parameters?
... result = quote123(foo)
fmt.Println(result)
// Output: "foo"
_ = convert(foo) // confirm foo satisfies convert at runtime
// fails due to argument type
// _ = convert(func(x float64) string { return "" })
}
Play: http://play.golang.org/p/XNMtrDUDS0
Tour: https://tour.golang...
What is the difference between currying and partial application?
...ints that other peoples examples of currying are not currying, but are actually just partial application.
14 Answers
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find() with nil when there are no records
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Yes, just do:
Challenge.find_by_id(10)
For Rails 4 and 5:
Challenge.find_by(id: 10)
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Accurate way to measure execution times of php scripts
...otime — Return current Unix timestamp with microseconds
If get_as_float is set to TRUE, then microtime() returns a float, which represents the current time in seconds since the Unix epoch accurate to the nearest microsecond.
Example usage:
$start = microtime(true);
while (...) {
}
$...
Allowed characters in filename [closed]
Where can I find a list of allowed characters in filenames, depending on the operating system?
(e.g. on Linux, the character : is allowed in filenames, but not on Windows)
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How to map and remove nil values in Ruby
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Ruby 2.7+
There is now!
Ruby 2.7 is introducing filter_map for this exact purpose. It's idiomatic and performant, and I'd expect it to become the norm very soon.
For example:
numbers = [1, 2, 5, 8, 10, 13]
enum.filter_map { |i| i * 2 if i.even? }
# => [4, 16, 20]
In your ...
Can not connect to local PostgreSQL
...
This really looks like a file permissions error. Unix domain sockets are files and have user permissions just like any other. It looks as though the OSX user attempting to access the database does not have file permissions to acce...
Declare a block method parameter without using a typedef
...ssue benefits from multiple):
@implementation CallbackAsyncClass {
void (^_loginCallback) (NSDictionary *response);
}
// …
- (void)loginWithCallback:(void (^) (NSDictionary *response))handler {
// Do something async / call URL
_loginCallback = Block_copy(handler);
// response will c...
Improve INSERT-per-second performance of SQLite
...more memory will be used for your database.
If you have indices, consider calling CREATE INDEX after doing all your inserts. This is significantly faster than creating the index and then doing your inserts.
You have to be quite careful if you have concurrent access to SQLite, as the whole database i...