How can i detect device current paired BLE's services ?

Hello everyone, i work at BLE device on swift. I have a problem to CoreBluetooth side. When my IOS device and BLE device not pairing , i got open my IOS App , app found my BLE device and be pair. But i closing my app when paired BLE to IOS device, i open my IOS App, app can't find my BLE and BLE's services. But IOS device and BLE device paired. How can i detect my BLE in my app when IOS device and BLE devices paired ?
How can i detect device current paired BLE's services ?
 
 
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