casting | Delegate methods in Ruby and preserve self | Application Framework library
kandi X-RAY | casting Summary
kandi X-RAY | casting Summary
Delegate methods in Ruby and preserve self. Add behaviors to your objects without altering their superclass hierarchy.
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Top functions reviewed by kandi - BETA
- Call the next method .
- Initialize object
- Assigns the module to the given module .
- Get the instance of the delegated method
- Perform attribute delegating method .
- Get a list of delegated attributes
- Checks if the given method is missing .
- Fetches the user s public methods
- Uncast object from object
- Returns an array of items from the collection
casting Key Features
casting Examples and Code Snippets
Lines of Code : 52
License : No License
Copy// => this.reviewScore = 9;
// bad
const totalScore = new String(this.reviewScore); // typeof totalScore is "object" not "string"
// bad
const totalScore = this.reviewScore + ''; // invokes this.reviewScore.valueOf()
// bad
const totalScore = t connection = mysql.createConnection({
typeCast: function (field, next) {
if (field.type === 'TINY' && field.length === 1) {
return (field.string() === '1'); // 1 = true, 0 = false
} else {
return next();
}
}
});
Community Discussions
Trending Discussions on casting
QUESTION
I want to Edit data, so for that, I should display it in a form.
In my table in the database, I have a primary key named id_casting
So I have he following code :
My script :
...ANSWER
Answered 2021-Jun-15 at 22:38By default laravel thinks that id is the primary key in your table. To fix this you would have to a primary key variable in your model
QUESTION
Hey guys given the example below in C when operating on a 64bit system as i understand, a pointer is 8 byte. Wouldn't the calloc here allocate too little memory as it takes the sizeof(int) which is 4 bytes? Thing is, this still works. Does it overwrite the memory? Would love some clarity on this.
Bonus question: if i remove the type casting (int*) i sometimes get a warning "invalid conversion from 'void*' to 'int*', does this mean it still works considering the warning?
...ANSWER
Answered 2021-Jun-15 at 21:19calloc is allocating the amount of memory you asked for on the heap. The pointer is allocated by your compiler either in registers or on the stack. In this case, calloc is actually allocating enough memory for 4 ints on the heap (which on most systems is going to be 16 bytes, but for the arduino uno it would be 8 because the sizeof(int) is 2), then storing the pointer to that allocated memory in your register/stack location.
For the bonus question: Arduino uses C++ instead of C, and that means that it uses C++'s stronger type system. void * and int * are different types, so it's complaining. You should cast the return value of malloc when using C++.
QUESTION
In C++20, we got the capability to sleep on atomic variables, waiting for their value to change.
We do so by using the std::atomic::wait method.
Unfortunately, while wait has been standardized, wait_for and wait_until are not. Meaning that we cannot sleep on an atomic variable with a timeout.
Sleeping on an atomic variable is anyway implemented behind the scenes with WaitOnAddress on Windows and the futex system call on Linux.
Working around the above problem (no way to sleep on an atomic variable with a timeout), I could pass the memory address of an std::atomic to WaitOnAddress on Windows and it will (kinda) work with no UB, as the function gets void* as a parameter, and it's valid to cast std::atomic to void*
On Linux, it is unclear whether it's ok to mix std::atomic with futex. futex gets either a uint32_t* or a int32_t* (depending which manual you read), and casting std::atomic to u/int* is UB. On the other hand, the manual says
The uaddr argument points to the futex word. On all platforms, futexes are four-byte integers that must be aligned on a four- byte boundary. The operation to perform on the futex is specified in the futex_op argument; val is a value whose meaning and purpose depends on futex_op.
Hinting that alignas(4) std::atomic should work, and it doesn't matter which integer type is it is as long as the type has the size of 4 bytes and the alignment of 4.
Also, I have seen many places where this trick of combining atomics and futexes is implemented, including boost and TBB.
So what is the best way to sleep on an atomic variable with a timeout in a non UB way? Do we have to implement our own atomic class with OS primitives to achieve it correctly?
(Solutions like mixing atomics and condition variables exist, but sub-optimal)
...ANSWER
Answered 2021-Jun-15 at 20:48You shouldn't necessarily have to implement a full custom atomic API, it should actually be safe to simply pull out a pointer to the underlying data from the atomic and pass it to the system.
Since std::atomic does not offer some equivalent of native_handle like other synchronization primitives offer, you're going to be stuck doing some implementation-specific hacks to try to get it to interface with the native API.
For the most part, it's reasonably safe to assume that first member of these types in implementations will be the same as the T type -- at least for integral values [1]. This is an assurance that will make it possible to extract out this value.
... and casting
std::atomictou/int*is UB
This isn't actually the case.
std::atomic is guaranteed by the standard to be Standard-Layout Type. One helpful but often esoteric properties of standard layout types is that it is safe to reinterpret_cast a T to a value or reference of the first sub-object (e.g. the first member of the std::atomic).
As long as we can guarantee that the std::atomic contains only the u/int as a member (or at least, as its first member), then it's completely safe to extract out the type in this manner:
QUESTION
I have a diamond inheritance structure in my code in which I have a pointer to the bottom object. I tried to case this to a pointer to the left of the two diamond sides, cast it again to the top of the diamond, and again to the right side. But apparently, C++ kind of remembers the order of casting and things don't work as expected. Example code:
...ANSWER
Answered 2021-Jun-14 at 08:50You can see the desired result by changing the last casting to:
QUESTION
I am really newbie in Flutter and SQLite. I need to store some data got from a DB into a global variable (in this code it's a local variable just for exemplification) and I don't know:
- where is the best point I can do it (now I put it in the homepage's initState method);
- how I can store future data in a no-future variable.
Below is the method for the data extraction
...ANSWER
Answered 2021-Jun-14 at 03:46Reading from database is an asynchronous activity, which means the query doesn't return some data immediately. so you have to wait for the operation to complete and then assign it to a variable.
QUESTION
I'm trying to do a very simple thing - casting a static list of inherited class objects to a list of base class objects. For some reason - in the result, I always get the inherited class objects. I can see that it isn't converting even when debugging inside the lambda expressions. What Am I missing here ?
See my code:
This is the class that contains the static property:
...ANSWER
Answered 2021-Jun-13 at 09:43While you are up-casting and down-casting within the type hierarchy, the true runtime type of the object remains intact. What you are doing is called a reference conversion. It only changes the type of the reference that points to the object in memory. The actual object remains untouched. Unlike value types, where type conversion involves changing the object identity, like an int to float conversion, casting only changes the type of the reference.
From the Microsoft Docs C# Language Reference:
Reference conversions, implicit or explicit, never change the referential identity of the object being converted. In other words, while a reference conversion may change the type of the reference, it never changes the type or value of the object being referred to.
If you are logging the list elements to the console and seeing InheritedClass, it is because Object.ToString() is defined like this:
QUESTION
In the below code, why does the compiler agree on casting a base class to a derived class knowing the object is purely a base one? How can print2() be called although it's a derived function? Can you tell me please what happens exactly from the point of view of a compiler/memory manager?
...ANSWER
Answered 2021-Jun-13 at 16:06This is undefined behavior, no diagnostic required.
A compiler has no obligation to report a compilation error for every possible programming bug. The only required diagnostic is when the program is ill-formed.
There's nothing technically wrong with the static_cast itself, with that statement alone. It follows all the requisite rules. The fact that it is used improperly, and results on the undefined behavior due to an earlier statement does not require an error message from the compiler. The new statement, and the static_cast itself could be in completely separate .cpp files (with a function call in between, one function calling new, and passing the result as a parameter to the function in the other .cpp file that does the static_cast). This is logically identical to the shown code. How could the compiler possibly be able to report an error, when it's compiling the other .cpp file, and has no knowledge of what's happening in the first one?
It is true that some compilers might be able to detect this bug and issue a warning message (possibly only with certain optimization levels enabled), but there is no obligation to do so.
QUESTION
I'm trying to store data into a database and I encountered a situation where I don't know is it feasible or not to do that.
so I have two following tables in the database
...ANSWER
Answered 2021-Jun-12 at 15:24your problem is in Carbon method, not in model, check the data passed to
QUESTION
This is the .XML code for email, similar is for password and other fields.
...ANSWER
Answered 2021-Jun-12 at 14:28You can use TextInputLayout to show an error to the user. It seems what you want to do is get the text from the input field, which is the EditText. What you need to do is give the EditText an id, and then reference it in your Java code, instead of the TextInputLayout. So you can move your id from the TextInputLayout and put it on the EditText instead like below:
QUESTION
I am creating a remote api using spring tool suite api and when running my code I keep getting an error. Been trying to figure out the problem, for hours but can't seem to figure it out.
Error Message:
...ANSWER
Answered 2021-Jun-11 at 18:24The error messsage already describes what's wrong:
Caused by: java.lang.ClassCastException: class org.springframework.http.HttpHeaders cannot be cast to class lombok.var (org.springframework.http.HttpHeaders and lombok.var are in unnamed module of loader 'app')
Here, you are trying to cast the HttpHeaders to var type. var is not a type(a class)
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