Question

我将Objective-C应用程序重写为Swift，并面临将此Objective-C代码转换为Swift的问题。

Objective-C代码：

for ( void(^block)(void) in enumerator.allObjects) {
    if (block)
        block();
}

Swift Code：

for (var block: () -> Void in enumerator.allObjects) {
        if (block) {
            block();
        }
    }

Xcode显示3个错误：

预期表达

＆＃39;＆＃39;中的预期条件声明

预期＆＃39;;＆＃39;在＆＃39;为＆＃39;声明

非常感谢; - ）

Answer 1

取出括号

  1> for i in 1...3 {
  2.     println(i) 
  3. } 
1
2
3
  4> for (i in 1...3) {
  5.     println(i) 
  6. } 
repl.swift:4:8: error: expected ';' in 'for' statement
for (i in 1...3) {
       ^
repl.swift:4:8: error: expected condition in 'for' statement
for (i in 1...3) {
       ^
repl.swift:4:8: error: expected ';' in 'for' statement
for (i in 1...3) {
       ^
repl.swift:4:8: error: expected expression
for (i in 1...3) {
       ^
repl.swift:4:8: error: expected ')' in 'for' statement
for (i in 1...3) {
       ^
repl.swift:4:5: note: to match this opening '('
for (i in 1...3) {
    ^
repl.swift:4:8: error: expected '{' in 'for' statement
for (i in 1...3) {
       ^
repl.swift:4:18: error: statement cannot begin with a closure expression
for (i in 1...3) {
                 ^
repl.swift:4:18: note: explicitly discard the result of the closure by assigning to '_'
for (i in 1...3) {
                 ^
                 _ = 
repl.swift:4:18: error: braced block of statements is an unused closure
for (i in 1...3) {
                 ^

  4>

Answer 2

这很有效。

let block1 : (Int)->() = { i in
    println(i)
}
let block2 : (Int)->() = { i in
    println(i*2)
}

let array = [block1, block2]

for block in array {
    block(1)
}

Swift中的Objective-C块

2 个答案: