目標C - 被刪除後的約束返回

我已經使用Interface Builder爲視圖添加了約束。後來在運行中，我需要刪除它們並添加新的。這是我如何更新約束：目標C - 被刪除後的約束返回

for (UIView *view in _fromProduitView.subviews) { 
       [view removeConstraints:view.constraints]; 
      for (NSLayoutConstraint *constraint in _fromProduitView.constraints) { 
       if ([[constraint firstItem] isKindOfClass:[UILabel class]]) { 
        [_fromProduitView removeConstraint:constraint]; 
       } 
      } 
    } 
    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_fonctionLabel attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:_fromProduitView attribute:NSLayoutAttributeCenterX multiplier:1 constant:0]]; 
    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_fonctionLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:_fromProduitView attribute:NSLayoutAttributeLeading multiplier:1.0f constant:16]]; 

    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_artisanNameLabel attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:_fromProduitView attribute:NSLayoutAttributeCenterX multiplier:1 constant:0]]; 
    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_artisanNameLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:_fonctionLabel attribute:NSLayoutAttributeBottom multiplier:1.0f constant:8]]; 

    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_supplierAccrocheLabel attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:_fromProduitView attribute:NSLayoutAttributeCenterX multiplier:1 constant:0]]; 
    [_fromProduitView addConstraint:[NSLayoutConstraint constraintWithItem:_supplierAccrocheLabel attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:_artisanNameLabel attribute:NSLayoutAttributeBottom multiplier:1.0f constant:8]];

在這一點上，我記錄的觀點_fromProductView這是上海華盈的約束：

<__NSArrayI 0x7fdc2df84cc0>(
<NSLayoutConstraint:0x7fdc2dfa2d40 UIView:0x7fdc2dfa59e0.height == 0>, 
<NSLayoutConstraint:0x7fdc2db32320 UILabel:0x7fdc2dfa4730.centerX == UIView:0x7fdc2dfa59e0.centerX>, 
<NSLayoutConstraint:0x7fdc2e9f3210 UILabel:0x7fdc2dfa4730.top == UIView:0x7fdc2dfa59e0.leading + 16>, 
<NSLayoutConstraint:0x7fdc2df84960 UILabel:0x7fdc2dfb0d60.centerX == UIView:0x7fdc2dfa59e0.centerX>, 
<NSLayoutConstraint:0x7fdc2cff0b90 UILabel:0x7fdc2dfb0d60.top == UILabel:0x7fdc2dfa4730.bottom + 8>, 
<NSLayoutConstraint:0x7fdc2e9f38b0 UILabel:0x7fdc2dfa4c30.centerX == UIView:0x7fdc2dfa59e0.centerX>, 
<NSLayoutConstraint:0x7fdc2e9f4390 UILabel:0x7fdc2dfa4c30.top == UILabel:0x7fdc2dfb0d60.bottom + 8> 
)

這是我想要的方式，但問題是後來的約束上我已經刪除回來衝突我已經創建視圖消失其結果的那些：

<__NSArrayI 0x7fdc2b5f7460>(
<NSLayoutConstraint:0x7fdc2dfa2d40 UIView:0x7fdc2dfa59e0.height == 0>, 
<NSLayoutConstraint:0x7fdc2e9f3210 UILabel:0x7fdc2dfa4730.top == UIView:0x7fdc2dfa59e0.leading + 16>, 
<NSLayoutConstraint:0x7fdc2df84960 UILabel:0x7fdc2dfb0d60.centerX == UIView:0x7fdc2dfa59e0.centerX>, 
<NSLayoutConstraint:0x7fdc2e9f38b0 UILabel:0x7fdc2dfa4c30.centerX == UIView:0x7fdc2dfa59e0.centerX>, 
<NSLayoutConstraint:0x7fdc2dfa2de0 UILabel:0x7fdc2dfa4730.centerX == UIView:0x7fdc2dfa59e0.centerX - 8>, 
<NSLayoutConstraint:0x7fdc2dfa2e30 UILabel:0x7fdc2dfa4730.leading == UILabel:0x7fdc2dfb0d60.leading>, 
<NSLayoutConstraint:0x7fdc2dfa2ed0 UILabel:0x7fdc2dfb0d60.top == UILabel:0x7fdc2dfa4730.bottom + 2>, 
<NSLayoutConstraint:0x7fdc2dfa2f70 UILabel:0x7fdc2dfa4c30.leading == UILabel:0x7fdc2dfb0d60.leading>, 
<NSLayoutConstraint:0x7fdc2dfa2fc0 UILabel:0x7fdc2dfa4c30.top == UILabel:0x7fdc2dfb0d60.bottom>, 
<NSLayoutConstraint:0x7fdc2cff0b90 UILabel:0x7fdc2dfb0d60.top == UILabel:0x7fdc2dfa4730.bottom + 8>, 
<NSLayoutConstraint:0x7fdc2e9f4390 UILabel:0x7fdc2dfa4c30.top == UILabel:0x7fdc2dfb0d60.bottom + 8>, 
<NSLayoutConstraint:0x7fdc2db32320 UILabel:0x7fdc2dfa4730.centerX == UIView:0x7fdc2dfa59e0.centerX> 
)

所以主要是，我不明白如何永久刪除約束以及如何在添加新約束時更新視圖

來源

2016-10-06 Haroun SMIDA

如果您刪除所有約束，可能是您不應該從一開始就將它們添加到IB中？ –

嘗試先禁用約束，然後應用新約束。您可以通過將'active'屬性設置爲'NO'來簡單地禁用約束。 –

我沒有刪除所有的約束，'superView'包含了旁邊的其他視圖。除此之外，這種情況只有在遇到一些「罕見」情況時纔會發生。 –

爲要刪除的約束創建出口。嘗試停用您的約束而不是刪除象下面這樣：

yourconstraint.active = YES;

後以編程方式分配新的約束到視圖，並呼籲要求的視以下方法：

[self updateConstraints];

來源

2016-10-06 10:57:07

好的，我會試試看。 –

目標C - 被刪除後的約束返回

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