badoo/Chatto

Constraints problem when adding DemoChatViewController as a child view controller

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#494 opened on Jun 27, 2018

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Description

I am trying to add DemoChatViewController(subclass of BaseChatViewController) into a view as a child view controller:

addChildViewController(child) child.view.translatesAutoresizingMaskIntoConstraints = false view.addSubview(child.view) child.didMove(toParentViewController: self)

view.addConstraints([ NSLayoutConstraint(item: child.view, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 0), NSLayoutConstraint(item: child.view, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0), NSLayoutConstraint(item: child.view, attribute: .leading, relatedBy: .equal, toItem: view, attribute: .leading, multiplier: 1, constant: 0), NSLayoutConstraint(item: child.view, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: .trailing, multiplier: 1, constant: 0) ])

But I got runtime error: Unable to simultaneously satisfy constraints. "<_UILayoutSupportConstraint:0x600000285960 _UILayoutSpacer:0x6000005cce40'UIVC-topLayoutGuide'.height == 0 (active)>", "<_UILayoutSupportConstraint:0x600000284f60 V:|-(0)-[_UILayoutSpacer:0x6000005cce40'UIVC-topLayoutGuide'] (active, names: '|':Chatto.BaseChatViewControllerView:0x7fa67342a940 )>", "<NSAutoresizingMaskLayoutConstraint:0x604000093ce0 h=-&- v=-&- UIView:0x7fa67342a560.height == UIView:0x7fa67342a750.height (active)>", "<NSAutoresizingMaskLayoutConstraint:0x604000288e80 h=--& v=--& UIView:0x7fa673373520.height == 0 (active)>", "<NSLayoutConstraint:0x60000009ea50 V:[_UILayoutSpacer:0x6000005cce40'UIVC-topLayoutGuide']-(>=0)-[UIView:0x7fa66df6f110] (active)>", "<NSLayoutConstraint:0x600000284d30 V:[UIView:0x7fa66df6f110]-(0)-| (active, names: '|':Chatto.BaseChatViewControllerView:0x7fa67342a940 )>", "<NSLayoutConstraint:0x6040002972a0 UIView:0x7fa66b613d30.height == 44 (active)>", "<NSLayoutConstraint:0x604000483cf0 V:|-(0)-[ChattoAdditions.ExpandableTextView:0x7fa66c167000] (active, names: '|':ChattoAdditions.ChatInputBar:0x7fa67323d040 )>", "<NSLayoutConstraint:0x604000480000 V:[ChattoAdditions.ExpandableTextView:0x7fa66c167000]-(0)-[UIView:0x7fa66b613d30] (active)>", "<NSLayoutConstraint:0x604000486810 V:[UIView:0x7fa66b613d30]-(0)-| (active, names: '|':ChattoAdditions.ChatInputBar:0x7fa67323d040 )>", "<NSLayoutConstraint:0x604000093ec0 UIView:0x7fa66df6f110.top == ChattoAdditions.ChatInputBar:0x7fa67323d040.top (active)>", "<NSLayoutConstraint:0x604000287530 V:[ChattoAdditions.ChatInputBar:0x7fa67323d040]-(0)-| (active, names: '|':UIView:0x7fa66df6f110 )>", "<NSLayoutConstraint:0x604001286bd0 V:|-(0)-[Chatto.BaseChatViewControllerView:0x7fa67342a940] (active, names: '|':UIView:0x7fa67342a560 )>", "<NSLayoutConstraint:0x604001286b30 Chatto.BaseChatViewControllerView:0x7fa67342a940.bottom == UIView:0x7fa67342a560.bottom (active)>", "<NSLayoutConstraint:0x60000029c660 V:|-(0)-[UIView:0x7fa67342a750] (active, names: '|':UIView:0x7fa673373520 )>", "<NSLayoutConstraint:0x60000009f6d0 UIView:0x7fa67342a750.bottom == UIView:0x7fa673373520.bottom (active)>" )

Will attempt to recover by breaking constraint <NSLayoutConstraint:0x6040002972a0 UIView:0x7fa66b613d30.height == 44 (active)>

Any suggestion? Thanks in advance. Cheers

Contributor guide

Tech stack
swift
Domain
mobile
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
iOS developmentAuto LayoutSwift
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the Auto Layout constraints in DemoChatViewController and its parent view controller. The error indicates conflicting constraints involving the top layout guide and chat input bar. Check if the child view controller's view uses layout guides that conflict with the parent's constraints. Consider using safe area layout guides or adjusting constraint priorities.