正文
Swift - 下标脚本方法介绍及实例
小程序：扫一扫查出行【扫一扫了解最新限行尾号】
复制小程序
定义下标脚本之后，可以使用“[]”来存取数据类型的值。
示例1：实现一个我们自定的字符串类，可以方便的通过索引获取某一个字符值，或某一部分字符串。同时也可以通过索引，给某一部分赋值。
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class
SubString
{
var
str:
String
=
""
init
(str:
String
)
{
self
.str = str;
}
/**下标脚本：获取/设置部分字符串**/
subscript(start:
Int
, length:
Int
) ->
String
{
get
{
return
(str
as
NSString
).substringWithRange(
NSRange
(location: start, length: length))
}
set
{
var
tmp =
Array
(str)
str =
""
var
s =
""
var
e =
""
for
(idx, item)
in
enumerate
(tmp) {
if
(idx < start)
{
s +=
"\(item)"
}
if
(idx >= start + length)
{
e +=
"\(item)"
}
}
str = s + newValue + e
}
}
/**下标脚本：获取/设置字符**/
subscript(index:
Int
) ->
String
{
get
{
return
String
(
Array
(str)[index])
}
set
{
var
tmp =
Array
(str)
tmp[index] =
Array
(newValue)[0]
str =
""
for
(idx, item)
in
enumerate
(tmp) {
str +=
"\(item)"
}
}
}
}
var
str =
SubString
(str:
"hangge.com"
)
println
(str[7,3])
//获取字符串：com
println
(str[7])
//获取字符：c
str[7,3] =
"COM"
//设置部分字符串
str[0] =
"H"
//设置部分字符
println
(str[0,10])
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示例1改进：通过类扩展，也可以直接给String类添加索引功能，代码如下：
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extension
String
{
subscript(start:
Int
, length:
Int
) ->
String
{
get
{
return
(
self
as
NSString
).substringWithRange(
NSRange
(location: start, length: length))
}
set
{
var
tmp =
Array
(
self
)
var
s =
""
var
e =
""
for
(idx, item)
in
enumerate
(tmp) {
if
(idx < start)
{
s +=
"\(item)"
}
if
(idx >= start + length)
{
e +=
"\(item)"
}
}
self
= s + newValue + e
}
}
subscript(index:
Int
) ->
String
{
get
{
return
String
(
Array
(
self
)[index])
}
set
{
var
tmp =
Array
(
self
)
tmp[index] =
Array
(newValue)[0]
self
=
""
for
(idx, item)
in
enumerate
(tmp) {
self
+=
"\(item)"
}
}
}
}
var
str =
"hangge.com"
println
(str[7,3])
println
(str[7])
str[7,3] =
"COM"
str[0] =
"H"
println
(str[0,10])
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示例2：使用一维数组结合下标方法一定程度上模拟实现了二维数组
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class
Matrix
{
let
rows:
Int
, columns:
Int
var
grid: [
Double
]
init
(rows:
Int
, columns:
Int
) {
self
.rows = rows
self
.columns = columns
grid =
Array
(count: rows * columns, repeatedValue: 0.0)
}
func
indexIsValidForRow(row:
Int
, column:
Int
) ->
Bool
{
return
row >= 0 && row < rows && column >= 0 && column < columns
}
subscript(row:
Int
, column:
Int
) ->
Double
{
get
{
assert(indexIsValidForRow(row, column: column),
"Index out of range"
)
return
grid[(row * columns) + column]
}
set
{
assert(indexIsValidForRow(row, column: column),
"Index out of range"
)
grid[(row * columns) + column] = newValue
}
}
}
var
value =
Matrix
(rows: 20,columns: 20)
value[10,10] = 20
println
(value)
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