@Published публикует новое значение, прежде чем оно фактически изменит сохраненное значение. Я не знаю, почему Apple реализовала это таким образом.
Вот разборка метода установки Published, который публикует уведомление, а затем сохраняет новое значение. По адресу 462e7 публикует уведомление по телефону Combine.CurrentValueSubject.send(A) -> (). Позже, по адресу 4635f, он изменяет сохраненное значение, вызывая swift_modifyAtReferenceWritableKeyPath.
_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZTf4ngdgd_n: // function signature specialization <Arg[1] = Owned To Guaranteed, Arg[2] = Dead, Arg[3] = Owned To Guaranteed, Arg[4] = Dead> of static Combine.Published.subscript.setter : <A where A1: AnyObject>(_enclosingInstance: A1, wrapped: Swift.ReferenceWritableKeyPath<A1, A>, storage: Swift.ReferenceWritableKeyPath<A1, Combine.Published<A>>) -> A
00000000000461b0 push rbp ; CODE XREF=_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZ+22, _$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluiMZ.resume.0+126, _$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluiMZ.resume.0+244
00000000000461b1 mov rbp, rsp
00000000000461b4 push r15
00000000000461b6 push r14
00000000000461b8 push r13
00000000000461ba push r12
00000000000461bc push rbx
00000000000461bd sub rsp, 0x48
00000000000461c1 mov r13, rdx
00000000000461c4 mov r15, rsi
00000000000461c7 mov qword [rbp+var_40], rdi
00000000000461cb mov rax, qword [rdx]
00000000000461ce mov rcx, qword [_$ss24ReferenceWritableKeyPathCMo_fc4a8] ; _$ss24ReferenceWritableKeyPathCMo_fc4a8
00000000000461d5 mov rcx, qword [rcx]
00000000000461d8 mov r14, qword [rax+rcx+8]
00000000000461dd mov rax, qword [r14-8]
00000000000461e1 mov rax, qword [rax+0x40]
00000000000461e5 add rax, 0xf
00000000000461e9 and rax, 0xfffffffffffffff0
00000000000461ed mov r12, rsp
00000000000461f0 sub r12, rax
00000000000461f3 mov rsp, r12
00000000000461f6 mov rbx, rsp
00000000000461f9 sub rbx, rax
00000000000461fc mov rsp, rbx
00000000000461ff mov qword [rbp+var_70], rsi
0000000000046203 mov rdi, rsi
0000000000046206 call imp___stubs__swift_unknownObjectRetain ; swift_unknownObjectRetain
000000000004620b lea rdi, qword [rbp+var_70]
000000000004620f mov rax, rbx
0000000000046212 mov qword [rbp+var_48], r13
0000000000046216 mov rsi, r13
0000000000046219 call imp___stubs__swift_getAtKeyPath ; swift_getAtKeyPath
000000000004621e movsxd rax, dword [r14+0x20]
0000000000046222 mov r13, qword [rbx+rax]
0000000000046226 test r13, r13
0000000000046229 je loc_46269
000000000004622b mov qword [rbp+var_50], r15
000000000004622f mov r15, qword [r14+0x10]
0000000000046233 mov rdi, r13 ; argument "instance" for method imp___stubs__swift_retain
0000000000046236 call imp___stubs__swift_retain ; swift_retain
000000000004623b mov rdi, rbx ; argument #1 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
000000000004623e mov qword [rbp+var_38], r15
0000000000046242 mov rsi, r15 ; argument #2 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
0000000000046245 mov r15, qword [rbp+var_50]
0000000000046249 mov rdx, r14 ; argument #3 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
000000000004624c call _$s7Combine9PublishedVyxGRld__Cr__lWOh ; outlined destroy of Combine.Published<A>
0000000000046251 call _$s7Combine25ObservableObjectPublisherC4sendyyF ; Combine.ObservableObjectPublisher.send() -> ()
0000000000046256 mov rdi, r13 ; argument "instance" for method imp___stubs__swift_release
0000000000046259 call imp___stubs__swift_release ; swift_release
000000000004625e mov rdi, qword [rbp+var_70]
0000000000046262 call imp___stubs__swift_unknownObjectRelease ; swift_unknownObjectRelease
0000000000046267 jmp loc_46284
loc_46269:
0000000000046269 mov rdi, r15 ; CODE XREF=_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZTf4ngdgd_n+121
000000000004626c call imp___stubs__swift_unknownObjectRelease ; swift_unknownObjectRelease
0000000000046271 mov rsi, qword [r14+0x10] ; argument #2 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
0000000000046275 mov rdi, rbx ; argument #1 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
0000000000046278 mov qword [rbp+var_38], rsi
000000000004627c mov rdx, r14 ; argument #3 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
000000000004627f call _$s7Combine9PublishedVyxGRld__Cr__lWOh ; outlined destroy of Combine.Published<A>
loc_46284:
0000000000046284 mov qword [rbp+var_70], r15 ; CODE XREF=_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZTf4ngdgd_n+183
0000000000046288 mov rdi, r15
000000000004628b call imp___stubs__swift_unknownObjectRetain ; swift_unknownObjectRetain
0000000000046290 mov rbx, qword [rbp+var_48]
0000000000046294 mov rdi, rbx ; argument "instance" for method imp___stubs__swift_retain
0000000000046297 call imp___stubs__swift_retain ; swift_retain
000000000004629c lea rdi, qword [rbp+var_70]
00000000000462a0 mov rax, r12
00000000000462a3 mov rsi, rbx
00000000000462a6 call imp___stubs__swift_getAtKeyPath ; swift_getAtKeyPath
00000000000462ab movsxd rdi, dword [r14+0x1c]
00000000000462af cmp qword [r12+rdi], 0x0
00000000000462b4 je loc_46317
00000000000462b6 add rdi, r12 ; argument #1 for method _$s7Combine9PublishedV9PublisherVyx_GRld__Cr__lWOc
00000000000462b9 lea rsi, qword [rbp+var_30] ; argument #2 for method _$s7Combine9PublishedV9PublisherVyx_GRld__Cr__lWOc
00000000000462bd call _$s7Combine9PublishedV9PublisherVyx_GRld__Cr__lWOc ; outlined init with copy of Combine.Published<A>.Publisher
00000000000462c2 mov rdi, r12 ; argument #1 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
00000000000462c5 mov rbx, qword [rbp+var_38]
00000000000462c9 mov rsi, rbx ; argument #2 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
00000000000462cc mov rdx, r14 ; argument #3 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
00000000000462cf call _$s7Combine9PublishedVyxGRld__Cr__lWOh ; outlined destroy of Combine.Published<A>
00000000000462d4 mov r13, qword [rbp+var_30]
00000000000462d8 mov rdi, r13 ; argument "instance" for method imp___stubs__swift_retain
00000000000462db call imp___stubs__swift_retain ; swift_retain
00000000000462e0 mov r12, qword [rbp+var_40]
00000000000462e4 mov rdi, r12 ; argument #1 for method _$s7Combine19CurrentValueSubjectC4sendyyxF
00000000000462e7 call _$s7Combine19CurrentValueSubjectC4sendyyxF ; Combine.CurrentValueSubject.send(A) -> ()
00000000000462ec mov rdi, r13 ; argument "instance" for method imp___stubs__swift_release
00000000000462ef mov r13, rbx
00000000000462f2 mov rbx, qword [rbp+var_48]
00000000000462f6 call imp___stubs__swift_release ; swift_release
00000000000462fb lea rdi, qword [rbp+var_30] ; argument #1 for method _$s7Combine9PublishedV9PublisherVyx_GRld__Cr__lWOh
00000000000462ff call _$s7Combine9PublishedV9PublisherVyx_GRld__Cr__lWOh ; outlined destroy of Combine.Published<A>.Publisher
0000000000046304 mov rdi, qword [rbp+var_70]
0000000000046308 call imp___stubs__swift_unknownObjectRelease ; swift_unknownObjectRelease
000000000004630d mov rdi, rbx ; argument "instance" for method imp___stubs__swift_release
0000000000046310 call imp___stubs__swift_release ; swift_release
0000000000046315 jmp loc_4633d
loc_46317:
0000000000046317 mov rdi, r15 ; CODE XREF=_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZTf4ngdgd_n+260
000000000004631a call imp___stubs__swift_unknownObjectRelease ; swift_unknownObjectRelease
000000000004631f mov rdi, rbx ; argument "instance" for method imp___stubs__swift_release
0000000000046322 call imp___stubs__swift_release ; swift_release
0000000000046327 mov rdi, r12 ; argument #1 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
000000000004632a mov r13, qword [rbp+var_38]
000000000004632e mov rsi, r13 ; argument #2 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
0000000000046331 mov rdx, r14 ; argument #3 for method _$s7Combine9PublishedVyxGRld__Cr__lWOh
0000000000046334 call _$s7Combine9PublishedVyxGRld__Cr__lWOh ; outlined destroy of Combine.Published<A>
0000000000046339 mov r12, qword [rbp+var_40]
loc_4633d:
000000000004633d mov qword [rbp+var_30], r15 ; CODE XREF=_$s7Combine9PublishedV18_enclosingInstance7wrapped7storagexqd___s24ReferenceWritableKeyPathCyqd__xGAHyqd__ACyxGGtcRld__CluisZTf4ngdgd_n+357
0000000000046341 mov rdi, r15
0000000000046344 call imp___stubs__swift_unknownObjectRetain ; swift_unknownObjectRetain
0000000000046349 mov rdi, rbx ; argument "instance" for method imp___stubs__swift_retain
000000000004634c call imp___stubs__swift_retain ; swift_retain
0000000000046351 lea r14, qword [rbp+var_70]
0000000000046355 lea rsi, qword [rbp+var_30]
0000000000046359 mov rdi, r14
000000000004635c mov rdx, rbx
000000000004635f call imp___stubs__swift_modifyAtReferenceWritableKeyPath ; swift_modifyAtReferenceWritableKeyPath
0000000000046364 mov r15, rax
0000000000046367 mov rdi, rdx
000000000004636a mov rax, qword [r13-8]
000000000004636e mov rsi, r12
0000000000046371 mov rdx, r13
0000000000046374 call qword [rax+0x28]
0000000000046377 mov rdi, r14
000000000004637a xor esi, esi
000000000004637c call r15
000000000004637f mov rdi, qword [rbp+var_30]
0000000000046383 call imp___stubs__swift_unknownObjectRelease ; swift_unknownObjectRelease
0000000000046388 mov rdi, rbx ; argument "instance" for method imp___stubs__swift_release
000000000004638b call imp___stubs__swift_release ; swift_release
0000000000046390 lea rsp, qword [rbp+var_28]
0000000000046394 pop rbx
0000000000046395 pop r12
0000000000046397 pop r13
0000000000046399 pop r14
000000000004639b pop r15
000000000004639d pop rbp
000000000004639e ret