design-pattern | 设计模式学习配套代码 | Architecture library

You need to replace page by _doc (or remove it altogether) as there's no more mapping types

Like h5py, PyTables (aka tables) can also create and read HDF5 files. Pandas uses PyTables "under the hood" to create and read HDF5 files. PyTables has some useful search features to do exactly what you want to do. For completeness, I included a brief summary at the end of this answer that compares each package.

Here is an example I created to demonstrate the search behavior using your dataframe (dictionary) data.

To create the HDF5 file:
Note: most of the "work" creating the HDF5 file is (re)organizing your dictionary data into a NumPy recarray. The process can be simplified if the data structure is modified (shifting dictionary key/value levels) -- that assumes the structure isn't set yet.
Summary of steps:

1. Create a np.dtype that defines the fields (columns) of data.
2. Determine recarray rows by counting the number of dictionary items associated to each primary key.
3. Create a recarray of zeros with 1 and 2 above.
4. Loop thru the dictionary and map keys and values to appropriate row and field(column) name.

Code below:

The comment from @user207421 is spot on. If a language does not natively support double dispatch, no design pattern can alter the language to make it so. A pattern merely provides an alternative which may solve some of the problems that double dispatch would be applied to in another language.

People learning the Visitor Pattern who already have an understanding of double dispatch may be assisted by explanations such as, "Visitor solves a similar set of problems to those solved by double dispatch". Unfortunately, that explanation is often reduced to, "Visitor implements double dispatch" which is not true.

The fact you've recognized this means you have a solid understanding of both concepts already.

To address one part of your question: the relationship between Context and Strategy in the Strategy pattern. The UML diagram you see in books etc. is just a sample implementation, and this usually shows just the link from Context and Strategy. However the Strategy has to know something about its Context to do its job and this is usually passed as arguments in the method invocation on the Strategy object. When there are many arguments to pass, they may be replaced by passing a reference to the Context object to the Strategy constructor. This decision is an example of 'tailoring a pattern to fit its context'.

Normally, when people talk about using composition vs. inheritance, they are talking about alternative ways of solving the same problem. In both cases, a "base class" provides an implementation of an interface that you want to reuse in your "derived class"

When you implement this with inheritance, there is an undesirable is-a relationship between the derived class and the base class, with the effect that implementation details of the base class, which should be hidden, can become changes in the derived class class.

When you implement this with composition -- a real composition relationship -- the "derived" only has an is-a relationship with the interface that it wants to implement, and the cost of this is that it must delegate calls to the "base" class.

In the Bridge pattern, which you reference, the goal is a little different. You do want to isolate the containing class from change to the connected implementation, but there is no is-a relationship between the containing class and an interface of the contained class.

The relationship between them may be one of composition, or may be simple aggregation -- that is an implementation detail. Often, the concrete implementation of the contained class will be injected as an interface into the containing class constructor, and in that case the relationship is just aggregation.

No, there is no access to a move from scoring code. That is by design - scoring needs to be independent of moves executed. Any solution has a score, and if two solutions represent the same state of the problem, their scores must equal - therefore the only thing that matters for the purposes of scoring is the state of the solution, not the state of the solver or any other external factor.

If you need to access a context in a ViewModel, you can use an AndroidViewModel, which lets you access an application context using getApplication(). You can use that to get things like a ContentResolver.

The cautionary note you listed is about not using or storing an activity, fragment, view, or other lifecycle component in the ViewModel - not really applicable to an application context (which is sometimes needed to get things like strings, or in your case, a ContentResolver, that are not tied to a view lifecycle).

Yes whenever you use new keyword to allocate some memory then you must always use delete to free up that memory later when no longer needed. Otherwise you will have a memory leak as in your program. In your case you should use delete inside the destructor in the MallarDuck.cpp .

Other solution would be to use smart pointers like unique_ptr so that you don't have to explicitly free the memory.

unique_ptr`'s syntax would something like:

In general, one needs to be very careful when looking at UML models for design patterns. There are three reasons:

• The reference for design patterns is the GoF. This book was published in 1995, before UML even existed, and used a variation of the OMT notation (an ancestor of UML). In case if doubts, this is the source to trust.
• The Java language design was made public in 1995, JDK 1.0 release in January 1996, and the language not yet widely known. The authors based their designs and code examples on a C++ class model, i.e. on classes and inheritance only, without bothering for multiple inheritance. Most modern languages do not support multiple inheritance. As a consequence, some of the original patterns have to be adapted for Java, C# or Swift, to make a distinction between classes, abstract classes and interfaces, and between inheritance and interface implementation. There are multiple ways to do this. For example, some systematically converted abstract classes to interfaces. Some converted them only when there was a conflict. And some converted according to the interface "spirit".
• Misunderstandings happen. Some people publish such diagrams on the net but misunderstand the pattern, or misunderstand UML, or both together. Also, Gamma et al started the book when they were PhD students and also made some mistakes. You'll find for example some inconcsitencies in their use of the OMT aggregation.
• The worst case is the Builder pattern, where you have not only those problems, but on top of that you have a naming conflict: a very popular Java book introduced a (very different) variant of the builder pattern, with a different intent and another design, which caused total confusion.

Now to your specific example, and based on the content you have provided:

• oodesign is the closest to the original pattern and fully accurate. Btw, I mostly use links to their pages when it comes to patterns.
• refactoring guru is also a good choice. They opted to use interfaces instead of abstract classes, which is fine. But they have redefined the interface's operations and properties (probably in relation to own examples) and require a bidirectional navigation that seems not justified. If you're interested, there is a "Head First: Design patterns" which uses a similar mapping but keeps the original interface.
• wikipedia is not bad either: they have left out the client (which the GoF showed in light gray, to suggest that it's not essential for this pattern); They are more precise and complete on dependencies; But they also redefined the operations and properties differently. And they added an unnecessary aggregation symbol.
• How to make it in Java is confusing, because they kept one abstract class and opted for an interface for the other. And they have hidden the operations and properties. But there's nothing fundamentally wrong at first sight.
• Forget about tutorial points, at least for this UML diagram. It's plain wrong, as @qwerty_so already mentioned in the comments.

The statement of accuracy is for this pattern only and for the current version of the content. This cannot be generalized to all the design patterns in view of my introductory remarks.