56 lines
1.6 KiB
Swift
56 lines
1.6 KiB
Swift
/// A container for template variables.
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public class Context {
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var dictionaries: [[String: Any]]
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let namespace: Namespace
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/// Initialise a Context with an optional dictionary and optional namespace
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public init(dictionary: [String: Any]? = nil, namespace: Namespace = Namespace()) {
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if let dictionary = dictionary {
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dictionaries = [dictionary]
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} else {
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dictionaries = []
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}
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self.namespace = namespace
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}
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public subscript(key: String) -> Any? {
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/// Retrieves a variable's value, starting at the current context and going upwards
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get {
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for dictionary in Array(dictionaries.reversed()) {
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if let value = dictionary[key] {
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return value
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}
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}
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return nil
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}
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/// Set a variable in the current context, deleting the variable if it's nil
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set(value) {
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if let dictionary = dictionaries.popLast() {
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var mutable_dictionary = dictionary
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mutable_dictionary[key] = value
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dictionaries.append(mutable_dictionary)
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}
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}
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}
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/// Push a new level into the Context
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fileprivate func push(_ dictionary: [String: Any]? = nil) {
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dictionaries.append(dictionary ?? [:])
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}
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/// Pop the last level off of the Context
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fileprivate func pop() -> [String: Any]? {
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return dictionaries.popLast()
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}
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/// Push a new level onto the context for the duration of the execution of the given closure
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public func push<Result>(dictionary: [String: Any]? = nil, closure: (() throws -> Result)) rethrows -> Result {
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push(dictionary)
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defer { _ = pop() }
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return try closure()
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}
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}
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