for tower in &mut game.towers {
tower.towers_attack(&mut game)
};
给出cannot borrow game as mutable more than once at a time [E0499]
我的代码正在运行，但我正在重构它以使其更有意义。
工作是什么（主要注意事项是，在游戏对象上可变地循环两次很好，但这是因为功能拥有“游戏”的所有权？）
impl Attack for Game {
fn towers_attack(&mut self) {
for tower in &mut self.towers {
tower.attacked = false;
if tower.hp.is_positive() {
for creep in &mut self.lane_creeps {
if tower.position.distance_between(creep.position) < 12.0 &&
creep.side != tower.side && !tower.attacked {
creep.hp -= tower.attack_damage as i32;
tower.attacked = true;
break;
}
}
}
}
}
}
game.towers_attack();
将第一个循环移到函数外部并在tower而不是game.tower上实现会导致问题。
我很困惑自己，我相信我只需要将game的所有权归还for tower in &mut game.towers { tower.towers_attack(&mut game) };然后在退出时归还所有权，因此如果我明确授予所有权，则不会发生借款，但是，我不确定这是否可行或有意义。
towers_attack功能
impl TowerAttack for Tower {
fn towers_attack(&mut self, game: &mut Game) {
self.attacked = false;
if self.hp.is_positive() {
for creep in &mut game.lane_creeps {
if self.position.distance_between(creep.position) < 12.0 &&
creep.side != self.side && !self.attacked {
creep.hp -= self.attack_damage as i32;
self.attacked = true;
break;
}
}
}
}
}
答案 0 :(得分：4)
new CheckboxCell(true, false) Rust会阻止此调用，因为public Widget test() {
DataGrid<DatagridType> grid = new DataGrid<DatagridType>();
final MultiSelectionModel<DatagridType> selectionModel = new MultiSelectionModel<DatagridType>(new ProvidesKey<DatagridType>() {
@Override
public Integer getKey(DatagridType item) {
return item.getRowId();
}
});
grid.setSelectionModel(selectionModel, DefaultSelectionEventManager.<DatagridType> createCheckboxManager());
selectionModel.addSelectionChangeHandler(new Handler() {
@Override
public void onSelectionChange(SelectionChangeEvent event) {
Window.alert(selectionModel.getSelectedSet().toString());
}
});
grid.addColumn(new Column<DatagridType, Boolean>(new CheckboxCell(true, false)) {
@Override
public Boolean getValue(DatagridType object) {
return selectionModel.isSelected(object);
}
@Override
public void render(Context context, DatagridType object, SafeHtmlBuilder sb) {
if(object.isActive())
super.render(context, object, sb);
}
}, "Select");
TextColumn<DatagridType> nameColumn = new TextColumn<DatagridType>() {
@Override
public String getValue(DatagridType object) {
return object.getEmpName();
}
};
TextColumn<DatagridType> idColumn = new TextColumn<DatagridType>() {
@Override
public String getValue(DatagridType object) {
return Integer.toString(object.getEmpId());
}
};
TextColumn<DatagridType> statusColumn = new TextColumn<DatagridType>() {
@Override
public String getValue(DatagridType object) {
return object.isActive() ? "Active" : "In Acticve";
}
};
grid.addColumn(nameColumn, "EMP Name");
grid.addColumn(idColumn, "EMP ID");
grid.addColumn(statusColumn, "Status");
List<DatagridType> values = new ArrayList<DatagridType>();
values.add(new DatagridType(0, "ABC", 1001, true));
values.add(new DatagridType(1, "ABC", 1001, false));
values.add(new DatagridType(2, "AAA", 1002, true));
values.add(new DatagridType(3, "AAA", 1002, false));
values.add(new DatagridType(4, "BBB", 1003, true));
values.add(new DatagridType(5, "BBB", 1003, false));
grid.setRowData(values);
grid.setHeight("500px");
Window.alert("Done");
return grid;
}
private class DatagridType {
private int rowId;
private String empName;
private int empId;
private boolean active;
public DatagridType(int rowId, String empName, int empId, boolean active) {
this.rowId = rowId;
this.empName = empName;
this.empId = empId;
this.active = active;
}
public int getRowId() {
return rowId;
}
public String getEmpName() {
return empName;
}
public int getEmpId() {
return empId;
}
public boolean isActive() {
return active;
}
@Override
public String toString() {
return Integer.toString(rowId);
}
}
的实现可能：
for tower in &mut game.towers {
tower.towers_attack(&mut game)
}
或者
towers_attack导致向量被重新分配，因此迭代器无效，这将导致坏事发生。
相反，将所需的项目子集传递给fn towers_attack(game: &mut Game) {
game.towers.clear()
}
。例如：
fn towers_attack(game: &mut Game) {
game.towers.push(...)
}
我只需要将游戏的所有权归为
towers_attack
您始终将表达式的所有权转移到fn towers_attack(lane_creeps: &mut Vec<Creeps>) { ... }
循环。在这种情况下，您将可变参考的所有权传递给for tower in &mut game.towers { tower.towers_attack(&mut game) };。
然后在退出时返回所有权
没有办法做到这一点; for循环不会返回任何内容。