Object functions

local M = require 'moses'

keys (obj)

Collects the names of an object attributes.

M.keys({1,2,3}) -- => "{1,2,3}"
M.keys({x = 0, y = 1}) -- => "{'y','x'}"

values (obj)

Collects the values of an object attributes.

M.values({1,2,3}) -- => "{1,2,3}"
M.values({x = 0, y = 1}) -- => "{1,0}"

path (obj, ...)

Returns the value at a given path in an object.

local entity = {
  pos = {x = 1, y = 2},
  engine = {
    left = {status = 'active', damage = 5},
    right = {status = 'off', damage = 10}
  },
  boost = false
}

M.path(entity,'pos','x') -- => 1
M.path(entity,'pos','y') -- => 2
M.path(entity,'engine','left','status') -- => 'active'
M.path(entity,'engine','right','damage') -- => 10
M.path(entity,'boost') -- => false

spreadPath (obj, ...)

Spreads object under property path onto provided object. It is similar to flattenPath, but removes object under the property path.

local obj = {a = 1, b = 2, c = {d = 3, e = 4, f = {g = 5}}}
M.spreadPath(obj, 'c', 'f')
-- => {a = 1, b = 2, d = 3, e = 4, g = 5, c = {f = {}}}

flattenPath (obj, ...)

Flattens object under property path onto provided object. It is similar to spreadPath, but preserves object under the property path.

local obj = {a = 1, b = 2, c = {d = 3, e = 4, f = {g = 5}}}
M.spreadPath(obj, 'c', 'f')
-- => {a = 1, b = 2, d = 3, e = 4, g = 5, c = {d = 3, e = 4, f = {g = 5}}}

kvpairs (obj)

Converts an object to an array-list of key-value pairs.

local obj = {x = 1, y = 2, z = 3}
M.each(M.kvpairs(obj), function(v,k)
	print(k, table.concat(v,','))	
end)

-- => 1	y,2
-- => 2	x,1
-- => 3	z,3

toObj (kvpairs)

Converts an array list of kvpairs to an object where keys are taken from the 1rst column in the kvpairs sequence, associated with values in the 2nd column.

local list_pairs = {{'x',1},{'y',2},{'z',3}}
obj = M.toObj(list_pairs)

-- => {x = 1, y = 2, z = 3}

invert (obj)

Aliases: mirror.

Switches key-value pairs:

M.invert {'a','b','c'} -- => "{a=1, b=2, c=3}"
M.invert {x = 1, y = 2} -- => "{'x','y'}"

property (key)

Returns a function that will return the key property of any passed-in object.

local who = M.property('name')
local people = {name = 'Henry'}
who(people) -- => 'Henry'

propertyOf (obj)

Returns a function that will return the key property of any passed-in object.

local people = {name = 'Henry'}
print(M.propertyOf(people)('name')) -- => 'Henry'

toBoolean (value)

Converts a given value to a boolean.

M.toBoolean(true) -- => true
M.toBoolean(false) -- => false
M.toBoolean(nil) -- => false
M.toBoolean({}) -- => true
M.toBoolean(1) -- => true

extend (destObj, ...)

Extends a destination object with the properties of some source objects.

M.extend({},{a = 'b', c = 'd'}) -- => "{a = 'b', c = 'd'}"

functions (obj [, recurseMt])

Aliases: methods.

Returns all functions names within an object.

M.functions(coroutine) 
-- => "{'yield','wrap','status','resume','running','create'}"

When given recurseMt, will also include obj metatable's functions.

local mt = {print = print}
local t = {assert = assert}
setmetatable(t, {__index = mt})
M.functions(t, true) -- => "{'assert','print'}"

clone (obj [, shallow])

Clones a given object.

local obj = {1,2,3}
local obj2 = M.clone(obj)
print(obj2 == obj) -- => false
print(M.isEqual(obj2, obj)) -- => true

tap (obj, f)

Invokes a given interceptor function on some object, and then returns the object itself. Useful to tap into method chaining to hook intermediate results. The passed-in interceptor should be prototyped as f(obj,...).

local v = M.chain({1,2,3,4,5,6,7,8,9,10})
  :filter(function(v) return v%2~=0 end) -- retain odd values
  :tap(function(v) print('Max is', M.max(v) end) -- Tap max value 
  :map(function(v) return v^2 end)
  :value() -- =>	 Max is 89

has (obj, key)

Checks if an object has a given attribute.

M.has(_,'has') -- => true
M.has(coroutine,'resume') -- => true
M.has(math,'random') -- => true

pick (obj, ...)

Aliases: choose.

Collects whilelisted properties of a given object.

local object = {a = 1, b = 2, c = 3}
M.pick(object,'a','c') -- => "{a = 1, c = 3}"

omit (obj, ...)

Aliases: drop.

Omits blacklisted properties of a given object.

local object = {a = 1, b = 2, c = 3}
M.omit(object,'a','c') -- => "{b = 2}"

template (obj [, template])

Aliases: defaults.

Applies a template on an object, preserving existing properties.

local obj = {a = 0}
M.template(obj,{a = 1, b = 2, c = 3}) -- => "{a=0, c=3, b=2}"

isEqual (objA, objB [, useMt])

Aliases: compare, M.matches.

Compares objects:

M.isEqual(1,1) -- => true
M.isEqual(true,false) -- => false
M.isEqual(3.14,math.pi) -- => false
M.isEqual({3,4,5},{3,4,{5}}) -- => false

result (obj, method)

Calls an object method, passing it as a first argument the object itself.

M.result('abc','len') -- => 3
M.result({'a','b','c'},table.concat) -- => 'abc'

isTable (t)

Is the given argument an object (i.e a table) ?

M.isTable({}) -- => true
M.isTable(math) -- => true
M.isTable(string) -- => true

isCallable (obj)

Is the given argument callable ?

M.isCallable(print) -- => true
M.isCallable(function() end) -- => true
M.isCallable(setmetatable({},{__index = string}).upper) -- => true
M.isCallable(setmetatable({},{__call = function() return end})) -- => true

isArray (obj)

Is the given argument an array (i.e. a sequence) ?

M.isArray({}) -- => true
M.isArray({1,2,3}) -- => true
M.isArray({'a','b','c'}) -- => true

isIterable (obj)

Checks if the given object is iterable with pairs.

M.isIterable({}) -- => true
M.isIterable(function() end) -- => false
M.isIterable(false) -- => false
M.isIterable(1) -- => false

type (obj)

Extends Lua's type function. It returns the type of the given object and also recognises 'file' userdata

M.type('string') -- => 'string'
M.type(table) -- => 'table'
M.type(function() end) -- => 'function'
M.type(io.open('f','w')) -- => 'file'

isEmpty ([obj])

Is the given argument empty ?

M.isEmpty('') -- => true
M.isEmpty({})  -- => true
M.isEmpty({'a','b','c'}) -- => false

isString (obj)

Is the given argument a string ?

M.isString('') -- => true
M.isString('Hello') -- => false
M.isString({}) -- => false

isFunction (obj)

Is the given argument a function ?

M.isFunction(print) -- => true
M.isFunction(function() end) -- => true
M.isFunction({}) -- => false

isNil (obj)

Is the given argument nil ?

M.isNil(nil) -- => true
M.isNil() -- => true
M.isNil({}) -- => false

isNumber (obj)

Is the given argument a number ?

M.isNumber(math.pi) -- => true
M.isNumber(math.huge) -- => true
M.isNumber(0/0) -- => true
M.isNumber() -- => false

isNaN (obj)

Is the given argument NaN ?

M.isNaN(1) -- => false
M.isNaN(0/0) -- => true

isFinite (obj)

Is the given argument a finite number ?

M.isFinite(99e99) -- => true
M.isFinite(math.pi) -- => true
M.isFinite(math.huge) -- => false
M.isFinite(1/0) -- => false
M.isFinite(0/0) -- => false

isBoolean (obj)

Is the given argument a boolean ?

M.isBoolean(true) -- => true
M.isBoolean(false) -- => true
M.isBoolean(1==1) -- => true
M.isBoolean(print) -- => false

isInteger (obj)

Is the given argument an integer ?

M.isInteger(math.pi) -- => false
M.isInteger(1) -- => true
M.isInteger(-1) -- => true

Object functions - Yonaba/Moses GitHub Wiki