|
| 1 | +--!strict |
| 2 | +--[=[ |
| 3 | + A very simple enum implementation that makes typechecking boilerplate simpler. |
| 4 | +
|
| 5 | + ```lua |
| 6 | + local require = require(script.Parent.loader).load(script) |
| 7 | +
|
| 8 | + local SimpleEnum = require("SimpleEnum") |
| 9 | +
|
| 10 | + export type MyEnumType = "none" | "always" |
| 11 | +
|
| 12 | + return SimpleEnum.new({ |
| 13 | + NONE = "none" :: "none", |
| 14 | + ALWAYS = "always" :: "always", |
| 15 | + }) |
| 16 | + ``` |
| 17 | +
|
| 18 | + @class SimpleEnum |
| 19 | +]=] |
| 20 | + |
| 21 | +local require = require(script.Parent.loader).load(script) |
| 22 | + |
| 23 | +local t = require("t") |
| 24 | + |
| 25 | +local SimpleEnum = {} |
| 26 | +SimpleEnum.ClassName = "SimpleEnum" |
| 27 | + |
| 28 | +export type EnumValue = any |
| 29 | + |
| 30 | +export type SimpleEnum<EnumMembers> = EnumMembers & { |
| 31 | + GetKeys: (self: SimpleEnum<EnumMembers>) -> { string }, |
| 32 | + GetValues: (self: SimpleEnum<EnumMembers>) -> { EnumValue }, |
| 33 | + GetMap: (self: SimpleEnum<EnumMembers>) -> EnumMembers, |
| 34 | + IsValue: (self: SimpleEnum<EnumMembers>, value: any) -> (boolean, string?), |
| 35 | + GetInterface: (self: SimpleEnum<EnumMembers>) -> (value: any) -> (boolean, string?), |
| 36 | +} |
| 37 | + |
| 38 | +export type PrivateSimpleEnum<EnumMembers> = |
| 39 | + typeof(setmetatable( |
| 40 | + {} :: { |
| 41 | + _members: { [string]: EnumValue }, |
| 42 | + }, |
| 43 | + {} :: typeof({ __index = SimpleEnum }) |
| 44 | + )) |
| 45 | + & SimpleEnum<EnumMembers> |
| 46 | + |
| 47 | +--[=[ |
| 48 | + Creates a new SimpleEnum. This is indexable like a normal table, BUT it is also |
| 49 | + type-checkable via `IsValue` and `GetInterface` and more. |
| 50 | +]=] |
| 51 | +function SimpleEnum.new<EnumMembers>(members: EnumMembers): SimpleEnum<EnumMembers> |
| 52 | + assert(type(members) == "table", "Members must be a table") |
| 53 | + |
| 54 | + local self: SimpleEnum<EnumMembers> = setmetatable({ |
| 55 | + _members = table.freeze(members), |
| 56 | + }, SimpleEnum) :: any |
| 57 | + |
| 58 | + for key, value in pairs(members :: any) do |
| 59 | + rawset(self, key, value) |
| 60 | + end |
| 61 | + |
| 62 | + return self |
| 63 | +end |
| 64 | + |
| 65 | +--[=[ |
| 66 | + Returns the list of enum keys. |
| 67 | +]=] |
| 68 | +function SimpleEnum.GetKeys<EnumMembers>(self: SimpleEnum<EnumMembers>): { string } |
| 69 | + local members: any = rawget(self, "_members") |
| 70 | + local keys = {} |
| 71 | + for key, _ in pairs(members) do |
| 72 | + table.insert(keys, key) |
| 73 | + end |
| 74 | + return keys |
| 75 | +end |
| 76 | + |
| 77 | +--[=[ |
| 78 | + Returns the list of enum values. |
| 79 | +]=] |
| 80 | +function SimpleEnum.GetValues<EnumMembers>(self: SimpleEnum<EnumMembers>): { EnumValue } |
| 81 | + local members: any = rawget(self, "_members") |
| 82 | + local values = {} |
| 83 | + for _, value in pairs(members) do |
| 84 | + table.insert(values, value) |
| 85 | + end |
| 86 | + return values |
| 87 | +end |
| 88 | + |
| 89 | +--[=[ |
| 90 | + Returns the map of enum members. |
| 91 | +]=] |
| 92 | +function SimpleEnum.GetMap<EnumMembers>(self: SimpleEnum<EnumMembers>): EnumMembers |
| 93 | + return rawget(self, "_members") :: EnumMembers |
| 94 | +end |
| 95 | + |
| 96 | +--[=[ |
| 97 | + Returns whether the value is a valid enum value. |
| 98 | +
|
| 99 | + ```lua |
| 100 | + local MyEnum = SimpleEnum.new({ |
| 101 | + FOO = "foo", |
| 102 | + BAR = "bar", |
| 103 | + }) |
| 104 | +
|
| 105 | + print(MyEnum:IsValue("foo")) --> true |
| 106 | + print(MyEnum:IsValue("baz")) --> false, "Expected one of: foo, bar; got baz" |
| 107 | + ``` |
| 108 | +]=] |
| 109 | +function SimpleEnum.IsValue<EnumMembers>(self: PrivateSimpleEnum<EnumMembers>, value: any): (boolean, string?) |
| 110 | + return self:GetInterface()(value) |
| 111 | +end |
| 112 | + |
| 113 | +--[=[ |
| 114 | + Returns a type-checking function for the enum. |
| 115 | +
|
| 116 | + ```lua |
| 117 | + local MyEnum = SimpleEnum.new({ |
| 118 | + FOO = "foo", |
| 119 | + BAR = "bar", |
| 120 | + }) |
| 121 | +
|
| 122 | + local typeChecker = MyEnum:GetInterface() |
| 123 | +
|
| 124 | + print(typeChecker("foo")) --> true |
| 125 | + print(typeChecker("baz")) --> false, "Expected one of: foo, bar; got baz" |
| 126 | + ``` |
| 127 | +]=] |
| 128 | +function SimpleEnum.GetInterface<EnumMembers>(self: PrivateSimpleEnum<EnumMembers>): (value: any) -> (boolean, string?) |
| 129 | + local found = rawget(self :: any, "_typeChecker") |
| 130 | + if found then |
| 131 | + return found |
| 132 | + end |
| 133 | + |
| 134 | + local typeChecker: any = t.valueOf(self:GetValues()) |
| 135 | + rawset(self :: any, "_typeChecker", typeChecker) |
| 136 | + return typeChecker |
| 137 | +end |
| 138 | + |
| 139 | +SimpleEnum.__index = function<EnumMembers>(self: PrivateSimpleEnum<EnumMembers>, index: string) |
| 140 | + if SimpleEnum[index] then |
| 141 | + return SimpleEnum[index] |
| 142 | + elseif self._members[index] then |
| 143 | + return self._members[index] |
| 144 | + else |
| 145 | + error(`'{tostring(self)}' has no member '{index}'`) |
| 146 | + end |
| 147 | +end |
| 148 | + |
| 149 | +SimpleEnum.__iter = function<EnumMembers>(self: PrivateSimpleEnum<EnumMembers>) |
| 150 | + return pairs(self._members) |
| 151 | +end |
| 152 | + |
| 153 | +SimpleEnum.__newindex = function<EnumMembers>(self: PrivateSimpleEnum<EnumMembers>, index: string) |
| 154 | + error(`Cannot assign to member '{index}' of enum '{tostring(self)}'`) |
| 155 | +end |
| 156 | + |
| 157 | +return SimpleEnum |
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