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This is tough. I can understand the problem, which is that block.type === configurator.blockType does not guard the types in way where TypeScript knows that configurator.value and block.config must be a matching pair.

Your current isConfigurableBlock check is only useful in this configureBlock function as a runtime safeguard. It is already known that all members of the DocumentBlock union are configurable as both IImageBlock and ITitleBlock extend IConfigurableDocumentBlock. So isConfigurableBlock(block) must always be true.

What we need to be checking is that the block variable is configurable by this specific configurator variable.

My first approach was to use a higher-order function to create a type guard that is specific to the configurator. This is a generic mess, asserts things that are beyond the scope of what's actually checked, and still doesn't work. For reference:

First, Disable the python command to open the windows store:

Search Manage app execution aliases and unselect App Installer of Python:

Second, You need to check which python you have installed your packages to:

And make sure in the VSCode you have selected the right interpreter(In the following picture, they are different).

This is called Template Method pattern.

This pattern allows children class to implement only the relevant bit of logic without the knowledge that is encapsulated in the parent class.

In your words, it allows every specific pizza store to define some characteristics of a pizza without knowing how the pizza must be prepared, baked, cutted, boxed.

You have some misunderstandings, and most of these are not related to Qt's abstraction classes, but to how these objects work in the GL itself:

Array.prototype.map() returns an array of elments returned from callback function. In your case it is an array:

Looks like you have things pretty well along!

You've misunderstood, at least in some parts. GCD is not "baked into the kernel", it's a library that runs on top of POSIX threads, which are OS-level primitives with kernel support. GCD is simply a set of APIs that make it easier for developers to do work on multiple threads without having to manage the threads themselves.

For what it's worth, you can see the source code for GCD. It's here: https://opensource.apple.com/tarballs/libdispatch/ That said, it's full of micro-optimizations that take advantage of obscure compiler features (branch prediction directives and things like that) and it can often be hard to read and understand, even for experienced systems programmers.

A full-detail explanation of GCD's inner workings is beyond the scope of a StackOverflow answer, but I'll try to cook up a one or two paragraph explanation.

GCD manages some number of POSIX threads behind the scenes that it will use to execute work in the desired way. It also maintains a number of data structures to organize that work, like "queues" which can be thought of as "lists of blocks of work to be done." There are also groups, which allow you to be notified when a list of work items is completed. There are also various IO mechanisms to allow asynchronous IO to be serviced with these work items. It may (or may not) use various kernel services (like threads, kqueues, etc) to manage parts of its workload, but those aren't specific to GCD.

At the end of the day though, there's little or nothing "special" or "blessed" about GCD. In fact, there are multiple ports of GCD to various other operating systems out there, like this one for Linux: http://nickhutchinson.github.io/libdispatch/ which should drive home the point that it's not something specific to the Darwin kernel. Put differently, you could write your own version of GCD from scratch without needing to recompile the kernel.