
## Preview Error

When you're using CoreData in a SwiftUI `View`, you'll get erros when resuming the preview with the following code.

```swift
struct ContentView: View {
  @Environment(\.managedObjectContext) var moc

  var body: some View {
    Text("hello World")
  }
}

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
  }
}

```

The reason is that your preview `ContentView()` does not have a managed object context.

## Solution

One solution I found is to create a wrapper view which adds test data to the managed object context and passes it back to the view.

```swift
struct PreviewCoreDataWrapper<Content: View>: View {
  let content: (NSManagedObjectContext) -> Content

  var body: some View {
    let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext

    let todo = Todo(context: managedObjectContext)
    todo.title = "I Am Legend"

    return self.content(managedObjectContext)
  }

  init(@ViewBuilder content: @escaping (NSManagedObjectContext) -> Content) {
    self.content = content
  }
}

```

Now, you can embed every view which needs access to the managed object context within the `PreviewCoreDataWrapper` view
and access the `managedObjectContext` to pass it into the enviroment.

```swift
struct MoviesView_Previews: PreviewProvider {
  static var previews: some View {
    PreviewCoreDataWrapper { managedObjectContext in
      MoviesView().environment(\.managedObjectContext, managedObjectContext)
    }
  }
}
```

Now you can resume your preview and it should render just fine without any errors.

---

<small>
  If you have feedback or questions, please feel free to get in touch via Twitter.
</small>


The SwiftUI preview errors when using CoreData managed object context.

SwiftUI Preview with CoreData


There are two ways to quickly add dark mode to your Tailwind CSS projects.
The first one is the quickest and easiest way. The second one is your choice if you want to have a controlled theme switch.

# 1. Screen Config

This is a little hack and you can't manually switch the theme as it detects the theme from the user's operating system.

## Set Config

Extend your `tailwind.config.js` theme by adding a new screen type.

```js
module.exports = {
  theme: {
    extend: {
      screens: {
        dark: { raw: '(prefers-color-scheme: dark)' },
      },
    },
  },
}
```

## Use Styles

You can now use it like you would use different screen sizes.

```html
<div class="text-gray-800 dark:bg-gray-200"></div>
```

It's also possible to add states like _hover_ into the dark mode.

```html
<div class="border-b hover:border-gray-800 dark:hover:border-gray-800"></div>
```

# 2. Plugin

Another, more clean way and with the possibility to switch the theme manually is the plugin [tailwindcss-dark-mode](https://github.com/ChanceArthur/tailwindcss-dark-mode)

Add the class `<html class="dark-mode">` to see the dark mode or remove it to see the regular theme.


There are two ways to introduce dark mode into your TailwindCSS projects.

Dark Mode in TailwindCSS


# Export to HTML

Go to [medium.com settings](https://medium.com/me/export) and request your export.

After a while, you'll get an email with a download link.
Download the `medium-export.zip` file and unpack it.

# Transform to MD

Inside the `medium-export` folder you'll find another folder `posts` with `.html` files in it.
To transform your `.html` files to `.md`, you can execute the `medium-2-md` NPM package with NPX.

```shell
npx medium-2-md convertLocal Downloads/medium-export/posts -f
```

Your posts in `.md` format can be found in the `medium-export/posts/md_*` folder


How to export your articles from medium.com into Markdown files.

Tips

Don't miss out.