109 lines
4.2 KiB
C++
109 lines
4.2 KiB
C++
// Copyright 2004-present Facebook. All Rights Reserved.
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#pragma once
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#include <folly/Conv.h>
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#include <folly/dynamic.h>
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#include "FollySupport.h"
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#include <exception>
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#include <string>
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// When building a cross-platform module for React Native, arguments passed
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// from JS are represented as a folly::dynamic. This class provides helpers to
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// extract arguments from the folly::dynamic to concrete types usable by
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// cross-platform code, and converting exceptions to a JsArgumentException so
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// they can be caught and reported to RN consistently. The goal is to make the
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// jsArgAs... methods at the end simple to use should be most common, but any
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// non-detail method can be used when needed.
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namespace facebook {
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namespace xplat {
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class JsArgumentException : public std::logic_error {
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public:
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JsArgumentException(const std::string& msg) : std::logic_error(msg) {}
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};
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// This extracts a single argument by calling the given method pointer on it.
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// If an exception is thrown, the additional arguments are passed to
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// folly::to<> to be included in the exception string. This will be most
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// commonly used when extracting values from non-scalar argument. The second
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// overload accepts ref-qualified member functions.
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template <typename R, typename... T>
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R jsArg(const folly::dynamic& arg, R (folly::dynamic::*asFoo)() const, const T&... desc);
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template <typename R, typename... T>
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R jsArg(const folly::dynamic& arg, R (folly::dynamic::*asFoo)() const&, const T&... desc);
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// This is like jsArg, but a operates on a dynamic representing an array of
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// arguments. The argument n is used both to index the array and build the
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// exception message, if any. It can be used directly, but will more often be
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// used by the type-specific methods following.
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template <typename R>
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R jsArgN(const folly::dynamic& args, size_t n, R (folly::dynamic::*asFoo)() const);
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template <typename R>
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R jsArgN(const folly::dynamic& args, size_t n, R (folly::dynamic::*asFoo)() const&);
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namespace detail {
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// This is a type helper to implement functions which should work on both const
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// and non-const folly::dynamic arguments, and return a type with the same
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// constness. Basically, it causes the templates which use it to be defined
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// only for types compatible with folly::dynamic.
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template <typename T>
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struct is_dynamic {
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typedef typename std::enable_if<std::is_assignable<folly::dynamic, T>::value, T>::type type;
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};
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} // end namespace detail
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// Easy to use conversion helpers are here:
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// Extract the n'th arg from the given dynamic, as a dynamic. Throws a
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// JsArgumentException if there is no n'th arg in the input.
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template <typename T>
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typename detail::is_dynamic<T>::type& jsArgAsDynamic(T&& args, size_t n);
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// Extract the n'th arg from the given dynamic, as a dynamic Array. Throws a
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// JsArgumentException if there is no n'th arg in the input, or it is not an
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// Array.
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template <typename T>
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typename detail::is_dynamic<T>::type& jsArgAsArray(T&& args, size_t n);
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// Extract the n'th arg from the given dynamic, as a dynamic Object. Throws a
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// JsArgumentException if there is no n'th arg in the input, or it is not an
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// Object.
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template <typename T>
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typename detail::is_dynamic<T>::type& jsArgAsObject(T&& args, size_t n);
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// Extract the n'th arg from the given dynamic, as a bool. Throws a
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// JsArgumentException if this fails for some reason.
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inline bool jsArgAsBool(const folly::dynamic& args, size_t n) {
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return jsArgN(args, n, &folly::dynamic::asBool);
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}
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// Extract the n'th arg from the given dynamic, as an integer. Throws a
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// JsArgumentException if this fails for some reason.
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inline int64_t jsArgAsInt(const folly::dynamic& args, size_t n) {
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return jsArgN(args, n, &folly::dynamic::asInt);
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}
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// Extract the n'th arg from the given dynamic, as a double. Throws a
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// JsArgumentException if this fails for some reason.
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inline double jsArgAsDouble(const folly::dynamic& args, size_t n) {
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return jsArgN(args, n, &folly::dynamic::asDouble);
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}
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// Extract the n'th arg from the given dynamic, as a string. Throws a
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// JsArgumentException if this fails for some reason.
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inline std::string jsArgAsString(const folly::dynamic& args, size_t n) {
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return facebook::react::detail::toStdString(jsArgN(args, n, &folly::dynamic::asString));
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}
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}}
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#include "JsArgumentHelpers-inl.h"
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