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43 lines
1.2 KiB
Lua

local Observable = require "rx.observable"
local util = require "rx.util"
--- Returns a new Observable that produces elements until the predicate returns falsy.
-- @arg {function} predicate - The predicate used to continue production of values.
-- @returns {Observable}
function Observable:takeWhile(predicate)
predicate = predicate or util.identity
return Observable.create(function(observer)
local taking = true
local subscription
local function onNext(...)
if taking then
util.tryWithObserver(observer, function(...)
taking = predicate(...)
end, ...)
if taking then
return observer:onNext(...)
else
if subscription then
subscription:unsubscribe()
end
return observer:onCompleted()
end
end
end
local function onError(message)
return observer:onError(message)
end
local function onCompleted()
return observer:onCompleted()
end
subscription = self:subscribe(onNext, onError, onCompleted)
return subscription
end)
end