Swift3.0 split函数切割字符串

我们先看函数的原型：

public func split(separator: Self.Iterator.Element, maxSplits: Int = default, omittingEmptySubsequences: Bool = default) -> [Self.SubSequence]

第一个参数就不用解释了，传入要切割的字符串，像这样

let line = "BLANCHE:   I don't want realism. I want magic!"
print(line.characters.split(separator: " ")
                     .map(String.init))
// Prints "["BLANCHE:", "I", "don\'t", "want", "realism.", "I", "want", "magic!"]"

下面看第二个参数，像这样，意思是切割几次，设置为1的话就把原来的字符串切成两个。

// The second example passes `1` for the `maxSplits` parameter, so the
// original string is split just once, into two new strings.

print(line.characters.split(separator: " ", maxSplits: 1)
                     .map(String.init))
// Prints "["BLANCHE:", "  I don\'t want realism. I want magic!"]"

第三个参数就很明确了，是否保留隐藏字符

// The final example passes `false` for the `omittingEmptySubsequences`
// parameter, so the returned array contains empty strings where spaces
// were repeated.

print(line.characters.split(separator: " ", omittingEmptySubsequences: false)
                      .map(String.init))
// Prints "["BLANCHE:", "", "", "I", "don\'t", "want", "realism.", "I", "want", "magic!"]"

看看官方文档对这三个参数的解释，懒得翻译了，也不是很难懂。

/// - Parameters:
///   - separator: The element that should be split upon.
///   - maxSplits: The maximum number of times to split the collection, or
///     one less than the number of subsequences to return. If
///     `maxSplits + 1` subsequences are returned, the last one is a suffix
///     of the original collection containing the remaining elements.
///     `maxSplits` must be greater than or equal to zero. The default value
///     is `Int.max`.
///   - omittingEmptySubsequences: If `false`, an empty subsequence is
///     returned in the result for each consecutive pair of `separator`
///     elements in the collection and for each instance of `separator` at
///     the start or end of the collection. If `true`, only nonempty
///     subsequences are returned. The default value is `true`.
/// - Returns: An array of subsequences, split from this collection's
///   elements.