Layout chaqirilmadan oldin constraintsda qanday o'zgarishlar qilish kerak?

Chegarlarni o'zgartirish layoutIfNeeded() chaqirilishidan oldin yoki tizim avtomatik ravishda layoutni chaqiradigan yangilash tsiklining yakunida amalga oshirilishi kerak. Eng keng tarqalgan usul — bu UIView yoki UIViewController.updateViewConstraints() ning updateConstraints() metodida.

updateConstraints() ichida chegaralarni o'zgartirish misoli:

override func updateConstraints() {
    // Chegara hali yaratilmagan yoki uning qiymatini o'zgartirish kerakligini tekshirish
    if myConstraint == nil {
        myConstraint = viewA.bottomAnchor.constraint(equalTo: viewB.topAnchor, constant: -8)
        myConstraint?.isActive = true // Chegarani faollashtirish
    }

    // Zarur bo'lsa, chegaraning qiymatini o'zgartirish
    myConstraint?.constant = someNewValue

    // Har doim super chaqirish
    super.updateConstraints()
}

Shuningdek, o'zgarishlar layoutIfNeeded() chaqirilishidan darhol oldin ham amalga oshirilishi mumkin, masalan, foydalanuvchi harakatiga yoki holat o'zgarishiga javoban:

// Mavjud cheklovni qiymatini o'zgartirish
someConstraint.constant = newValue

// O'zgarishlarni darhol qo'llash uchun layoutIfNeeded() chaqirish
view.layoutIfNeeded()

Muhim narsa shuki, constraintsdagi o'zgarishlar Auto Layout yangi ramkalarni hisoblash boshlashidan oldin tugallangan bo'lishi kerak.