Scala | StringContext

StringContext is the underlying mechanism that supports string interpolation in Scala. Whenever you use an interpolated string in Scala, the compiler implicitly uses the StringContext to process it. It offers a more extensible way to embed expressions within strings, and you can even define custom interpolators using it.

Here's a closer look at StringContext:

Basic Use: In its simplest form, string interpolation in Scala looks like this:
```
val name = "Alice"
val greeting = s"Hello, $name"
```
Behind the scenes, the above code is transformed by the compiler to:
```
val greeting = StringContext("Hello, ", "").s(name)
```
StringContext breaks the string literals and expressions apart, and then combines them using the .s method.
Other Built-in Interpolators: Scala comes with a few built-in interpolators like s, f, and raw. Each of these uses StringContext in the background.
- f interpolator is for formatted strings, similar to printf in other languages.
- raw interpolator is like the s interpolator, but it doesn��t escape literals.

Custom Interpolators: One of the powerful features of StringContext is the ability to define custom string interpolators.

For instance, consider an interpolator that turns a string into its ASCII representation:

implicit class StringContextOps(sc: StringContext) {
  def ascii(args: Any*): String = {
    val processed = sc.parts.zip(args).map { case (str, arg) =>
      str + arg.toString
    }.mkString + sc.parts.last
    processed.map(_.toInt).mkString(" ")
  }
}

val name = "AB"
println(ascii"This is $name")  // Will print ASCII values of the characters

The above code provides an ascii interpolator by adding an extension method to StringContext.

Safety & Escaping: One thing to be cautious about is avoiding injection attacks, especially if you're interpolating strings for SQL queries or generating scripts. Always ensure that interpolated values are appropriately escaped or, even better, avoid interpolating sensitive content entirely.

In summary, StringContext is a flexible and powerful way of dealing with string interpolations in Scala. While the built-in s, f, and raw interpolators cater to most use-cases, the ability to define custom interpolators makes it highly extensible and adaptable to different scenarios.

String Interpolation with StringContext in Scala:
String interpolation in Scala allows embedding variables and expressions into strings.
```
val name = "John"
val age = 30
val message = s"My name is $name and I'm $age years old."
```
Scala StringContext Example:
StringContext is used to define custom interpolators.
```
val amount = 25.5
val formatted = f"Total amount: $amount%.2f"
```
Advanced String Formatting in Scala with StringContext:
Advanced formatting using StringContext and interpolators.
```
val items = List("Apple", "Banana", "Orange")
val formattedList = list"${items.mkString(", ")}"
```

Scala StringContext vs Traditional String Interpolation:

Compare traditional string interpolation with Scala StringContext.

val name = "Alice"
val greeting = s"Hello, $name!"
// vs
val greetingCtx = stringContext("Hello, ", "!")
val result = greetingCtx(name)

Custom Interpolators with Scala StringContext:

Define custom interpolators for specialized string handling.

implicit class RepeatInterpolator(val sc: StringContext) extends AnyVal {
  def repeat(args: Any*): String = {
    val multiplier = 3
    sc.parts.mkString("") * multiplier
  }
}

val repeated = repeat"This will be repeated"

Dynamic SQL Queries with Scala StringContext:

Use StringContext for dynamic SQL queries.

val tableName = "employees"
val condition = "salary > 50000"
val sql = sql"SELECT * FROM $tableName WHERE $condition"

Scala StringContext and Compile-Time Safety:

Leverage compile-time safety with Scala StringContext.

val name = "John"
val age = 30
// Compile-time error if age is not an Int
val safeMessage = safe"My name is $name and I'm $age years old."

Interpolating Variables in Scala with StringContext:

Interpolate variables into strings using StringContext.

val language = "Scala"
val popularity = 5
val sentence = s"$language is popular with a rating of $popularity stars."

Creating Custom DSLs with Scala StringContext:
Build custom DSLs using StringContext for expressive syntax.
```
val person = person"Name: John, Age: 30, Occupation: Developer"
```