circular-dependency | 易学教程

How to avoid circular imports in Python? [duplicate]

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This question already has an answer here: Circular import dependency in Python 6 answers I know the issue of circular imports in python has come up many times before and I have read these discussions. The comment that is made repeatedly in these discussions is that a circular import is a sign of a bad design and the code should be reorganised to avoid the circular import. Could someone tell me how to avoid a circular import in this situation?: I have two classes and I want each class to have a constructor (method) which takes an instance of the other class and returns an instance of the class.

Circular dependency injection angular 2

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问题 I\'ve been struggling around injecting services into each other. The following blog Circular Dependency in constructors and Dependency Injection is kind of confusing where it says One of the two objects is hiding another object C I get the following error while injecting Service class into each other Can\'t resolve all parameters for PayrollService: (SiteService, StorageService, SweetAlertService, ?) //abstractmodal.service.ts @Injectable() export abstract class AbstractModel { abstract

Circular C++ Header Includes

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问题 In a project I have 2 classes: // mainw.h #include \"IFr.h\" ... class mainw { public: static IFr ifr; static CSize=100; ... }; // IFr.h #include \"mainw.h\" ... class IFr { public float[mainw::CSize]; }; But I cannot compile this code, getting an error at the static IFr ifr; line. Is this kind of cross-inclusion prohibited? 回答1: Is this kind of cross-inclusions are prohibited? Yes. A work-around would be to say that the ifr member of mainw is a reference or a pointer, so that a forward

Circular dependency in java classes

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问题 I have the following classes. public class B { public A a; public B() { a= new A(); System.out.println(\"Creating B\"); } } and public class A { public B b; public A() { b = new B(); System.out.println(\"Creating A\"); } public static void main(String[] args) { A a = new A(); } } As can be clearly seen, there is a circular dependency between the classes. if I try to run class A, I eventually get a StackOverflowError . If a dependency graph is created, where nodes are classes, then this

How to solve circular reference?

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问题 How do you solve circular reference problems like Class A has class B as one of its properties, while Class B has Class A as one of its properties? How to do architect for those kind of problems? If you take an example of NHibernate, there will be a parent-child relationship between objects. How is it able to handle those parent child scenarios? 回答1: In most cases when I've had to have two things reference each other, I've created an interface to remove the circular reference. For example:

Resolve build errors due to circular dependency amongst classes

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问题 I often find myself in a situation where I am facing multiple compilation/linker errors in a C++ project due to some bad design decisions (made by someone else :) ) which lead to circular dependencies between C++ classes in different header files (can happen also in the same file) . But fortunately(?) this doesn\'t happen often enough for me to remember the solution to this problem for the next time it happens again. So for the purposes of easy recall in the future I am going to post a

Circular References Cause Memory Leak?

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问题 I\'m trying to run down a memory leak in a windows forms application. I\'m looking now at a form which contains several embedded forms. What worries me is that the child forms, in their constructor, take a reference to the parent form, and keep it in a private member field. So it seems to me that come garbage-collection time: Parent has a reference to the child form, via the controls collection (child form is embedded there). Child form is not GC\'d. Child form has a reference to the parent

How to avoid circular imports in Python? [duplicate]

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问题 This question already has an answer here: Circular import dependency in Python 6 answers I know the issue of circular imports in python has come up many times before and I have read these discussions. The comment that is made repeatedly in these discussions is that a circular import is a sign of a bad design and the code should be reorganised to avoid the circular import. Could someone tell me how to avoid a circular import in this situation?: I have two classes and I want each class to have

Circular import dependency in Python

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问题 Let\'s say I have the following directory structure: a\\ __init__.py b\\ __init__.py c\\ __init__.py c_file.py d\\ __init__.py d_file.py In the a package\'s __init__.py , the c package is imported. But c_file.py imports a.b.d . The program fails, saying b doesn\'t exist when c_file.py tries to import a.b.d . (And it really doesn\'t exist, because we were in the middle of importing it.) How can this problem be remedied? 回答1: If a depends on c and c depends on a, aren't they actually the same

ImportError: Cannot import name X

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问题 I have four different files named: main, vector, entity and physics. I will not post all the code, just the imports, because I think that\'s where the error is. (If you want, I can post more) Main: import time from entity import Ent from vector import Vect #the rest just creates an entity and prints the result of movement Entity: from vector import Vect from physics import Physics class Ent: #holds vector information and id def tick(self, dt): #this is where physics changes the velocity and