if/guard case let

case : pattern matching.
let : binds associated values

⭐️ 注意： for case let ... where 加條件的方式跟 if/guard case let 不一樣❗️

// ⭐ if case let
//          ╭───── ⭐ pattern ─────╮    ↱ ⭐ value
if case let Media.movie(title, _, _) = movie { ... }

// ⭐ if case let
if case let .loaded(data) = state, 
   data.isEmpty                        // ⭐ additional conditions
{ ... }

// ⭐ guard case let
guard 
    case let .loaded(data) = state, 
    data.isEmpty                        // ⭐ additional conditions
else { ... }

it’s just a more compact syntax when pattern-matching against one case ...

// if case let
if case let pattern = value { ... }

// is equivalent to 
switch value { 
    case let pattern: ...
    // other cases
}

👉 alisoftware

// if case let
if case let .person(name, age) = joe { ... }
// is equivalent to
if case .person(let name, let age) = joe { ... }

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Last updated 4 years ago