Enums and Pattern Matching

Where Patterns

Pattern cases can add conditions with where.

Match and filter

where_patterns.swift 
enum Score {
    case points(Int)
}

let value = 
let score = Score.points(value)
var band = ""

switch score {
case Score.points(let amount) where amount >= 90:
    band = "excellent"
case Score.points(let amount) where amount >= 70:
    band = "steady"
case Score.points:
    band = "practice"
}

print("value=\(value)")
print("band=\(band)")

enum Score {
    case points(Int)
}

let value = 
let score = Score.points(value)
var band = ""

switch score {
case Score.points(let amount) where amount >= 90:
    band = "excellent"
case Score.points(let amount) where amount >= 70:
    band = "steady"
case Score.points:
    band = "practice"
}

print("value=\(value)")
print("band=\(band)")

enum Score {
    case points(Int)
}

let value = 
let score = Score.points(value)
var band = ""

switch score {
case Score.points(let amount) where amount >= 90:
    band = "excellent"
case Score.points(let amount) where amount >= 70:
    band = "steady"
case Score.points:
    band = "practice"
}

print("value=\(value)")
print("band=\(band)")
where A `where` clause refines a pattern after it has matched the shape of the value.