Dictionary is used to store unordered lists of values of the same type. Swift puts strict checking which does not allow you to enter a wrong type in a dictionary even by mistake. Dictionary uses a unique identifier known as a key to store a value which later can be referenced and looked up through the same key. Unlike items in an array, items in a dictionary do not have a specified order. You can use dictionary when you need to look up values based on their identifiers.
A dictionary key can be either integer or string without a restriction, but it should be unique within a dictionary.
If you assign a created dictionary to a variable then it’s always mutable which means you can change it by adding, removing, or changing its items but if you assign a dictionary to a constant then that dictionary is immutable, and its size and contents cannot be changed.You can create a empty dictionary of a certain type using the following initializer syntax: var Dict = [KeyType: ValueType]().We use this simple syntax to create an empty dictionary whose key will be of Int type and associated values will be strings: var someDict = [Int: String]().Following this example, you can create a dictionary from the given values: var Dict:[Int:String] = [4:”Four”, 5:”Five”, 6:”Six”].
To access a dictionary,we can retrieve a value from it by using subscript syntax, passing the key of the value you want to retrieve within square brackets immediately after the name of the dictionary as follows: var someVar = someDict[key].
We can modify dictionary using updateValue(forKey:) method to add an existing value to a given key of the dictionary. This method returns an optional value of the dictionary’s value type.
You can use removeValueForKey() method to remove a key-value pair from a dictionary. This method removes the key-value pair if it exists and returns the removed value, or returns nil if no value existed.
To Iterate over a dictionary, we can apply for-in loop to iterate over the entire set of key-value pairs in a dictionary .
To Convert a dictionary to Arrays we need to extract a list of key-value pairs from a given dictionary to build separate arrays for both keys and value.
You can use read-only count property of a dictionary to find out the number of items in an dictionary.
Finally you can use read-only empty property of a dictionary to find out whether a dictionary is empty or not.
A dictionary key can be either integer or string without a restriction, but it should be unique within a dictionary.
If you assign a created dictionary to a variable then it’s always mutable which means you can change it by adding, removing, or changing its items but if you assign a dictionary to a constant then that dictionary is immutable, and its size and contents cannot be changed.You can create a empty dictionary of a certain type using the following initializer syntax: var Dict = [KeyType: ValueType]().We use this simple syntax to create an empty dictionary whose key will be of Int type and associated values will be strings: var someDict = [Int: String]().Following this example, you can create a dictionary from the given values: var Dict:[Int:String] = [4:”Four”, 5:”Five”, 6:”Six”].
To access a dictionary,we can retrieve a value from it by using subscript syntax, passing the key of the value you want to retrieve within square brackets immediately after the name of the dictionary as follows: var someVar = someDict[key].
We can modify dictionary using updateValue(forKey:) method to add an existing value to a given key of the dictionary. This method returns an optional value of the dictionary’s value type.
You can use removeValueForKey() method to remove a key-value pair from a dictionary. This method removes the key-value pair if it exists and returns the removed value, or returns nil if no value existed.
To Iterate over a dictionary, we can apply for-in loop to iterate over the entire set of key-value pairs in a dictionary .
To Convert a dictionary to Arrays we need to extract a list of key-value pairs from a given dictionary to build separate arrays for both keys and value.
You can use read-only count property of a dictionary to find out the number of items in an dictionary.
Finally you can use read-only empty property of a dictionary to find out whether a dictionary is empty or not.