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40 lines
1.5 KiB
Lua
40 lines
1.5 KiB
Lua
local Observable = require "rx.observable"
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local util = require "rx.util"
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--- Returns a new Observable that produces values computed by accumulating the results of running a
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-- function on each value produced by the original Observable.
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-- @arg {function} accumulator - Accumulates the values of the original Observable. Will be passed
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-- the return value of the last call as the first argument and the
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-- current values as the rest of the arguments. Each value returned
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-- from this function will be emitted by the Observable.
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-- @arg {*} seed - A value to pass to the accumulator the first time it is run.
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-- @returns {Observable}
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function Observable:scan(accumulator, seed)
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return Observable.create(function(observer)
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local result = seed
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local first = true
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local function onNext(...)
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if first and seed == nil then
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result = ...
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first = false
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else
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return util.tryWithObserver(observer, function(...)
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result = accumulator(result, ...)
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observer:onNext(result)
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end, ...)
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end
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end
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local function onError(e)
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return observer:onError(e)
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end
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local function onCompleted()
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return observer:onCompleted()
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end
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return self:subscribe(onNext, onError, onCompleted)
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end)
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end
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