Characteristics with cached values must be read-only

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在用CoreBluetooth 做藍芽資料轉送時，把裝置設為周邊裝置報此錯誤：

Characteristics with cached values must be read-only

 

經查詢是因為在構造 Characteristic 時設定了 Value，根據官方說明，當Value 不是nil 時，只能設定為唯讀狀態。

 

Note: If you specify a value for the characteristic, the value is cached and its properties and permissions are set to be readable. Therefore, if you need the value of a characteristic to be writeable, or if you expect the value to change during the lifetime of the published service to which the characteristic belongs, you must specify the value to be nil. Following this approach ensures that the value is treated dynamically and requested by the peripheral manager whenever the peripheral manager receives a read or write request from a connected central

Characteristics with cached values must be read-only