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What does an underscore and interface name after keyword var mean?
(2 answers)
Closed 4 years ago.
Little bit confused with this code.
var _ QueryAppender = (*selectQuery)(nil)
I found this code in pg-go
repository and don't know why QueryAppender declared that way. Please explain me what is the use cases when I should declare variables that way.
This doesn't do anything at runtime, but unless the *selectQuery type satisfies the interface QueryAppender, compilation will fail. It's a kind of static assertion.
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Difference between http.Handle and http.HandleFunc?
(4 answers)
Closed 5 years ago.
I'm trying to understand the differences between Handle and HandleFunc.
Other than the differences, when would you use one over the other when building a Go web app?
https://golang.org/pkg/net/http/#Handle
You'd use whichever one fits your handler implementation. If you've implemented your handler as a function, you'd use HandleFunc; if you've implemented it as a type with a ServeHTTP method, you'd use Handle.
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What is the usefulness of `enable_shared_from_this`?
(6 answers)
Closed 5 years ago.
What is the point for a class T to inherit from std::enable_shared_from_this<T> ? I can't seem to figure out why you wouldn't just create a std::shared_ptr<this> ?
Cppreference has a good example on why.
If you want to return a std::shared_ptr of this while *this is already owned by a std::shared_ptr and you don't return shared_from_this() but return a new std::shared_ptr<T>(this) instead then you will end up with 2 shared pointers that don't know they're both owning the same object and thus the use_count() will be wrong which will cause a double delete, which is undefined behavior.
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
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I have been walking through the tutorials and know how to declare variables but can not find how to declare of variable as type Time.
How Time is declared in Go?
You will find plenty of example of Time variable declaration in the package time itself, as in the Duration example
t0 := time.Now()
This is using the "short variable declaration", which is a shorthand for a regular variable declaration with initializer expressions but no types.
This question already has answers here:
Closed 11 years ago.
Possible Duplicates:
Double colons rails
What does :: do?
I was reading a manual on Rails and came across this snippet:
match 'rocketeer.js' => ::TestRoutingMapper::RocketeerApp
I'd never seen the :: syntax at the head of a class name before. I'm wondering what is the significance of writing it this way.
See my answer to What does :: do?
This question already has answers here:
Closed 12 years ago.
Possible Duplicate:
When do you use the “this” keyword?
In OOP sometimes we can write this.PropertyName = VALUE and sometimes we can skip this. and just write PropertyName = VALUE.
My questions:
Should we try always to use this.?
Does using / writing this have any effect on application performance or does it just make the code a little bit clearer?
There shouldn't be any difference in performance. Its purely a style decision.