Creates a new dictionary with the specified capacity, then calls the given closure to initialize its contents.
SDK
- Xcode 11.2+
Framework
- Swift Standard Library
Declaration
init(_unsafeUninitializedCapacity capacity: Int, allowingDuplicates: Bool, initializingWith initializer: (UnsafeParameters
capacityThe capacity of the new dictionary.
allowingDuplicatesIf false, then the caller guarantees that all keys are unique. This promise isn’t verified – if it turns out to be false, then the resulting dictionary won’t be valid.
bodyA closure that can initialize the dictionary’s elements. This closure must return the count of the initialized elements, starting at the beginning of the buffer.
Discussion
Foundation uses this initializer to bridge the contents of an NSDictionary instance without allocating a pair of intermediary buffers. Pass the required capacity and a closure that can intialize the dictionary’s elements. The closure must return c, the number of initialized elements in both buffers, such that the elements in the range 0..<c are initialized and the elements in the range c..<capacity are uninitialized.
The resulting dictionary has a count less than or equal to c. The actual count is less iff some of the initialized keys were duplicates. (This cannot happen if allowing is false.)
The buffers passed to the closure are only valid for the duration of the call. After the closure returns, this initializer moves all initialized elements into their correct buckets.