> ## Documentation Index
> Fetch the complete documentation index at: https://algolia.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Highlighting

> Visually highlights matched terms in search results.

export const Index = () => <Tooltip tip="An Algolia index is a searchable dataset that consists of records and configuration settings. These settings define how the records are searched and ranked.">
    index
  </Tooltip>;

export const FlavorSwitcher = ({current, baseHref = "", options = [], label = "InstantSearch framework"}) => {
  if (options.length === 0) {
    return <div className="not-prose" role="alert" style={{
      margin: "0.25rem 0 1.5rem",
      padding: "0.75rem",
      border: "1px solid #f59e0b",
      borderRadius: "0.625rem",
      color: "inherit",
      fontSize: "0.875rem"
    }}>
        FlavorSwitcher requires at least one option.
      </div>;
  }
  const selected = options.find(option => option.value === current) ?? options[0];
  return <div className="not-prose mint-flavor-switcher">
      <style>{`
        .mint-flavor-switcher {
          --mfs-bg: #ffffff;
          --mfs-bg-hover: #f4f4f5;
          --mfs-bg-current: #eef2ff;
          --mfs-border: #d4d4d8;
          --mfs-fg: #18181b;
          --mfs-muted: #71717a;
          --mfs-accent: #4f46e5;
          position: relative;
          width: min(100%, 19rem);
          margin: 0.25rem 0 1.5rem;
          color: var(--mfs-fg);
          font-size: 0.875rem;
          line-height: 1.25rem;
        }

        .dark .mint-flavor-switcher {
          --mfs-bg: #18181b;
          --mfs-bg-hover: #27272a;
          --mfs-bg-current: #272747;
          --mfs-border: #3f3f46;
          --mfs-fg: #fafafa;
          --mfs-muted: #a1a1aa;
          --mfs-accent: #a5b4fc;
        }

        .mint-flavor-switcher details {
          position: relative;
        }

        .mint-flavor-switcher summary {
          display: flex;
          min-height: 2.75rem;
          box-sizing: border-box;
          align-items: center;
          justify-content: space-between;
          gap: 0.75rem;
          padding: 0.625rem 0.75rem;
          border: 1px solid var(--mfs-border);
          border-radius: 0.625rem;
          background: var(--mfs-bg);
          color: var(--mfs-fg);
          cursor: pointer;
          font-weight: 600;
          list-style: none;
          transition: border-color 150ms ease, box-shadow 150ms ease;
        }

        .mint-flavor-switcher summary::-webkit-details-marker {
          display: none;
        }

        .mint-flavor-switcher summary:hover {
          border-color: var(--mfs-accent);
        }

        .mint-flavor-switcher summary:focus-visible {
          outline: 2px solid var(--mfs-accent);
          outline-offset: 2px;
        }

        .mint-flavor-switcher__label {
          overflow: hidden;
          text-overflow: ellipsis;
          white-space: nowrap;
        }

        .mint-flavor-switcher__chevron {
          flex: none;
          transition: transform 150ms ease;
        }

        .mint-flavor-switcher details[open] .mint-flavor-switcher__chevron {
          transform: rotate(180deg);
        }

        .mint-flavor-switcher__menu {
          position: absolute;
          z-index: 50;
          top: calc(100% + 0.375rem);
          left: 0;
          width: 100%;
          box-sizing: border-box;
          margin: 0;
          padding: 0.375rem;
          border: 1px solid var(--mfs-border);
          border-radius: 0.625rem;
          background: var(--mfs-bg);
          box-shadow: 0 12px 30px rgb(0 0 0 / 16%);
          list-style: none;
        }

        .mint-flavor-switcher__menu li {
          margin: 0;
          padding: 0;
        }

        .mint-flavor-switcher__option {
          display: grid;
          gap: 0.125rem;
          padding: 0.625rem 0.75rem;
          border-radius: 0.4rem;
          color: var(--mfs-fg);
          text-decoration: none;
        }

        .mint-flavor-switcher__option:hover {
          background: var(--mfs-bg-hover);
        }

        .mint-flavor-switcher__option:focus-visible {
          outline: 2px solid var(--mfs-accent);
          outline-offset: -2px;
        }

        .mint-flavor-switcher__option[aria-current="page"] {
          background: var(--mfs-bg-current);
          color: var(--mfs-accent);
        }

        .mint-flavor-switcher__name {
          font-weight: 600;
        }

        .mint-flavor-switcher__description {
          color: var(--mfs-muted);
          font-size: 0.8125rem;
        }

        @media (prefers-reduced-motion: reduce) {
          .mint-flavor-switcher summary,
          .mint-flavor-switcher__chevron {
            transition: none;
          }
        }
      `}</style>

      <details>
        <summary aria-label={`${label}: ${selected.label}`}>
          <span className="mint-flavor-switcher__label">{selected.label}</span>
          <svg className="mint-flavor-switcher__chevron" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true">
            <path d="m6 9 6 6 6-6" />
          </svg>
        </summary>

        <ul className="mint-flavor-switcher__menu" aria-label={label}>
          {options.map(option => {
    const isCurrent = option.value === selected.value;
    const href = option.href ?? `${baseHref.replace(/\/$/, "")}/${encodeURIComponent(option.value)}`;
    return <li key={option.value}>
                <a className="mint-flavor-switcher__option" href={href} aria-current={isCurrent ? "page" : undefined}>
                  <span className="mint-flavor-switcher__name">
                    {option.label}
                  </span>
                  {option.description ? <span className="mint-flavor-switcher__description">
                      {option.description}
                    </span> : null}
                </a>
              </li>;
  })}
        </ul>
      </details>
    </div>;
};

<div className="mint-flavor-switcher-slot not-prose">
  <FlavorSwitcher
    current="ios"
    baseHref="/doc/api-reference/widgets/highlight"
    options={[
{ value: "js", label: "JavaScript", description: "InstantSearch.js" },
{ value: "react", label: "React", description: "React InstantSearch" },
{ value: "vue", label: "Vue", description: "Vue InstantSearch" },
{ value: "ios", label: "iOS", description: "InstantSearch iOS" },
{ value: "android", label: "Android", description: "InstantSearch Android" },
{ value: "flutter", label: "Flutter", description: "Algolia for Flutter" },
]}
  />
</div>

{/* vale Algolia.HeadingPronouns = NO */}

## About this widget

Displays the [highlighted attributes](/doc/guides/building-search-ui/ui-and-ux-patterns/highlighting-snippeting/ios) of your search results.

<Card title="Explore example code" icon="github" href="https://github.com/algolia/instantsearch-ios/tree/master/Examples/Showcase">
  Browse the Highlighting example code on GitHub.
</Card>

## Examples

Consider a movies <Index />.
Each movie record consists of two fields: `title` and `year`.
Algolia's response to the query "red" could look like:

```json JSON icon=braces theme={"system"}
{
  "title": "The Shawshank Redemption",
  "year": 1994,
  "objectID": "439817390",
  "_highlightResult": {
    "title": {
      "value": "The Shawshank <em>Red</em>emption",
      "matchLevel": "full",
      "fullyHighlighted": false,
      "matchedWords": ["red"]
    }
  }
}
```

Consider the `_highlightResult`'s value: `"The Shawshank <em>Red</em>emption"`.
The part of the string to highlight is marked with `<em>` tags or [your custom tags](/doc/guides/building-search-ui/ui-and-ux-patterns/highlighting-snippeting/ios#pre-and-post-tags).

`HighlightedString` is constructed with a raw tagged string, detects the tags and creates a `TaggedString`. This tagged string provides following properties:

* `input`. The input string.
* `output`. The input string without its tags.
* `taggedRanges`. A list of ranges defining highlighted ranges in `output`.

You can build a highlighted string in iOS is with an `NSAttributedString`.
InstantSearch provides `HighlightedString` and `NSAttributedString` extensions to simplify this.

```swift Swift icon=code theme={"system"}
let rawHighlightedString = "The Shawshank <em>Red</em>emption"
let highlightedString = HighlightedString(string: rawHighlightedString)

// Attributes to apply for a highlighted part of the string
let highLightingAttributes: [NSAttributedString.Key: Any] = [
  .foregroundColor: UIColor.red
]

// Create attributed string highlighted part of which is red
let attributedString = NSAttributedString(highlightedString: highlightedString, attributes: attributes)
```

The produced `NSAttributedString` can be assigned to a UIKit component that supports it.

```swift Swift icon=code theme={"system"}
let attributedString: NSAttributedString = ...
let label: UILabel = ...

label.attributedText = attributedString
```

The `Hit` wrapper structure uses the `HighlightedString` structure.
You can extract a highlighted string for an attribute using its `hightlightedString(forKey key: String)` function.

Example:

```swift Swift icon=code theme={"system"}
/* JSON search response
  {
    "title": "The Shawshank Redemption",
    "year": 1994,
    "objectID": "439817390",
    "_highlightResult": {
      "title": {
        "value": "The Shawshank <em>Red</em>emption",
        "matchLevel": "full",
        "fullyHighlighted": false,
        "matchedWords": [
          "red"
        ]
      },
    }
  }
*/

struct Movie: Codable {
  let title: String
  let year: Int
}

let movieHit: Hit<Movie> = ... /* parse JSON response */

let highlightedMovieTitle: HighlightedString? = movieHit.hightlightedString(forKey: "title")
```

You can read more about usage of the `Hit` wrapper structure in the [`Hits` reference](/doc/api-reference/widgets/hits/ios).