Dart 中常用的陣列操作方法總結

作者 三也視界

這位博主寫的很詳細到位，留下傳送門，感謝

dart 中常用的陣列操作方法總結

首先，我們準備兩組資料，以方便後面使用：

list

students =[,
,];list numbers =[2
,8,5
,1,7
,3];

foreach()

可以遍歷乙個陣列或者是乙個map

students.

foreach
((student)
=>
print
(student));
// // 
// map tom =
;tom.
foreach
((key, value)
=>
print
(key +
' - '
+ value.
tostring()
));// name - tom
// age - 16

可以用來操作已知陣列裡的每一項，然後返回乙個新陣列

var messages = students.

map(
(student)
=>
'hello '
+ student[
'name'])
.tolist()
;print
(messages)
;// [hello tom, hello jack, hello lucy]

用於判斷陣列是否包含某個元素

print

(students.
contains(5
));// true

var sum = numbers.

reduce
((curr, next)
=> curr + next)
;print
(sum)
;// 26
var sum2 = numbers.
fold(10
,(curr, next)
=> curr + next)
;print
(sum2)
;// 36

用於判斷陣列中的每一項是否均達到了某個條件

var isageover20 = students.

every
((student)
=> student[
"age"
]>20)
;print
(isageover20)
;// false
var isageover15 = students.
every
((student)
=> student[
"age"
]>15)
;print
(isageover15)
;// true

var ageover16 = students.

where
((student)
=> student[
"age"
]>16)
;print
(ageover16.
tolist()
);// [, ]
var agefirstover16 = students.
firstwhere
((student)
=> student[
"age"
]>
16, orelse:()
=> null)
;print
(agefirstover16)
;// 
var ageunder20 = students.
singlewhere
((student)
=> student[
"age"
]<
16, orelse:()
=> null)
;print
(ageunder20)
;// null

list arr =[1

,3,5
,2,7
,9];
print
(arr.
take(3
).tolist()
);// [1, 3, 5]
print
(arr.
skip(4
).tolist()
);// [7, 9]
print
(arr.
take(3
).skip(2
).take(1
).tolist()
);// [5]

轉殖乙個陣列

list arr =[1

,3,5
,2,7
,9];
var clonedarr = list.
from
(arr)
;print
(clonedarr)
;// [1, 3, 5, 2, 7, 9]

var arr1 =[[

2,5]
,[7]
,[11,
12]];
var flattened = arr1.
expand
((item)
=> item)
.tolist()
;print
(flattened)
;// [2, 5, 7, 11, 12]
var arr2 =[2
,5,8
];var computed = arr2.
expand
((item)
=>
[item *8]
).tolist()
;print
(computed)
;// [16, 40, 64]
// 當對每一項進行計算時類似於 map()
var computed2 = arr2.
map(
(item)
=> item *8)
.tolist()
;print
(computed2)
;// [16, 40, 64]

>var arr1 =[1

,3,5
,9,2
,1];
arr1.
add(10)
;print
(arr1)
;// [1, 3, 5, 9, 2, 1, 10]
arr1.
addall([
15,21]
);print
(arr1)
;// [1, 3, 5, 9, 2, 1, 10, 15, 21]

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