swift3 0字串擷取,字串處理

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1.擷取前面三個字串,要求輸出結果為abc

let str ="abcdefghi"

let index = str.index(str.startindex, offsetby:3)//獲取字元d的索引

let result = str.substring(to: index)//從起始擷取到索引的所有字串,即abc,注意不包含d

列印結果為 abc

2.擷取第四個開始的所有字串,要求輸出結果為defghi

let str = "abcdefghi"

let index = str.index(str.startindex, offsetby: 3)//獲取字元d的索引

let result = str.substring(from: index)//從d的索引開始擷取後面所有的字串即defghi

列印結果為defghi

3.擷取第4個開始的長度為2個字串,要求結果輸出為de

let str ="abcdefghi"

let startindex = str.index(str.startindex, offsetby:3)//獲取d的索引

let endindex = str.index(startindex, offsetby:2)//從d的索引開始往後兩個,即獲取f的索引

let result = str.substring(with: startindex..列印結果為de

4.判斷字串是否包含某段字元

let str = "abcdefghi"

let result = str.contains("ac")

列印結果為false

let result = str.contains("abc")

列印結果為true

5.字串大小寫轉換

let str = "abcdefghi"

let result = str.lowercased()

輸出結果為abcdefghi

let str = "abcdefghi"

let result = str.uppercased()

輸出結果為abcdefghi

6.指定字串替換為其他字串,將abc替換成m,使輸出結果為mdefghi

let str = "abcdefghi"

let result = str.replacingoccurrences(of:"abc", with: "m")

輸出結果為mdefghi

7.指定範圍內的字串替換為其他字串,將cde替換成m,使輸出結果為abmfghi

let str = "abcdefghi"

let startindex = str.index(str.startindex, offsetby:2)

let endindex = str.index(startindex, offsetby:3)

let result = str.replacingcharacters(in: startindex..輸出結果為abmfghi

8.有時候不確定字串的長度,需求為擷取字串末尾面開始往前5位,擷取長度為2的字串,使輸出為ef

let str = "abcdefghi"

let startindex = str.index(str.startindex, offsetby: str.lengthofbytes(using: .utf8) - 5)

let endindex = str.index(startindex, offsetby:2)

let result = str.substring(with: startindex..輸出結果為ef

9. 字串轉為陣列,使得輸出為["a", "b", "c", "d", "e", "f", "g", "h", "i"]

let str = "a.b.c.d.e.f.g.h.i"

let result = str.components(separatedby:".")

輸出為["a", "b", "c", "d", "e", "f", "g", "h", "i"]

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