LazyVStack & LazyHStack in SwiftUI | IOS | App Development | SwiftUI

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In SwiftUI, LazyVStack and LazyHStack are views that arrange their children in a line, either vertically for LazyVStack or horizontally for LazyHStack. What makes these views “lazy” is that they only render their children when they come into view, which is useful when dealing with a large number of child views that might not all be visible at once. This behavior contrasts with the more eager VStack and HStack, which instantiate their child views immediately.

Advantages:
Performance: When dealing with a large number of items, using the lazy variants can be more efficient since they only load views into memory as they are needed. This can reduce memory usage and improve scroll performance.

Dynamic Content: They are especially useful when the exact number of items or the content itself might be expensive to compute and isn’t known until runtime.

Limitations:
Size Calculations: Since views are only created when they are about to come on screen, some operations that require knowing the size or position of all children can’t be done as easily with the lazy variants as they could with their eager counterparts.

No Animations on Appear/Disappear: Because child views of a LazyVStack or LazyHStack are created and destroyed on-the-fly, you can’t apply appearance or disappearance animations to them.

Summary:
LazyVStack and LazyHStack are important tools in the SwiftUI toolkit, especially when optimizing for performance with large datasets. They help in creating more efficient UIs that adapt to the content they display. However, it’s essential to consider their limitations and use cases when deciding between the lazy variants and their eager counterparts (VStack and HStack).