var baseRest = require('./_baseRest'), createWrap = require('./_createWrap'), getHolder = require('./_getHolder'), replaceHolders = require('./_replaceHolders'); /** Used to compose bitmasks for function metadata. */ var BIND_FLAG = 1, BIND_KEY_FLAG = 2, PARTIAL_FLAG = 32; /** * Creates a function that invokes the method at `object[key]` with `partials` * prepended to the arguments it receives. * * This method differs from `_.bind` by allowing bound functions to reference * methods that may be redefined or don't yet exist. See * [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern) * for more details. * * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic * builds, may be used as a placeholder for partially applied arguments. * * @static * @memberOf _ * @since 0.10.0 * @category Function * @param {Object} object The object to invoke the method on. * @param {string} key The key of the method. * @param {...*} [partials] The arguments to be partially applied. * @returns {Function} Returns the new bound function. * @example * * var object = { * 'user': 'fred', * 'greet': function(greeting, punctuation) { * return greeting + ' ' + this.user + punctuation; * } * }; * * var bound = _.bindKey(object, 'greet', 'hi'); * bound('!'); * // => 'hi fred!' * * object.greet = function(greeting, punctuation) { * return greeting + 'ya ' + this.user + punctuation; * }; * * bound('!'); * // => 'hiya fred!' * * // Bound with placeholders. * var bound = _.bindKey(object, 'greet', _, '!'); * bound('hi'); * // => 'hiya fred!' */ var bindKey = baseRest(function(object, key, partials) { var bitmask = BIND_FLAG | BIND_KEY_FLAG; if (partials.length) { var holders = replaceHolders(partials, getHolder(bindKey)); bitmask |= PARTIAL_FLAG; } return createWrap(key, bitmask, object, partials, holders); }); // Assign default placeholders. bindKey.placeholder = {}; module.exports = bindKey;