Can't show the exact code.As the break point hit the function, I am trying to change its parameter value in debug pane like below: (lldb) po someVar "ABC" (lldb) expression self.someVar = "XYZ" () $R4 = {} (lldb) po self.someVar "XYZ" (lldb) po methodName(with: self.someVar) error: Execution was interrupted, reason: internal ObjC exception breakpoint(-10).. The process has been returned to the state before expression evaluation. (lldb)