Angular 2使用指令防止输入和模型更改 [英] Angular 2 Prevent input and model changing using directive
问题描述
我需要验证一个字段,使其仅包含范围内的数字.所以我试图写一条指令:
I need to validate a field to only have numbers in a range. So I have tried to write a directive:
@Directive({
selector: "[input-limitation]",
host: {
'(input)': 'onChange($event)',
}
})
export class InputLimitationDirective {
@Input("input-limitation") settings: InputLimitationSettings;
public constructor(private el: ElementRef) {
let self = this;
console.log(":::::::::::::::: el.nativeElement", el.nativeElement);
//jQuery(el.nativeElement).on('keypress', function (e) { self.onChange(e) });
};
private onChange($event) {
console.log("InputLimitationDirective", this.settings);
if (this.settings.InputType = "number") {
return this.numberLimitation($event);
}
}
private numberLimitation($event: any) {
let val: number = $event.target.value;
console.log("InputLimitationDirective", val);
console.log(val, this.settings.MinValue);
console.log(!val, val*1 < this.settings.MinValue*1);
if (!val || val*1 <= this.settings.MinValue*1) {
console.log("1 case");
event.preventDefault();
event.stopPropagation();
return false;
}
else if (val*1 >= this.settings.MaxValue*1) {
console.log("2 case");
event.preventDefault();
event.stopPropagation();
return false;
};
return true;
}
}
并以这种方式使用:
<input (change)="totalAmountChanged($event.target.value)"
[(ngModel)]="model.UsedVolume"
[disabled]="!isEditMode"
type="number"
[input-limitation]="usedVolumeInputLimitationsSettings"
pattern="^[1-9]\d*$" min="1" max="999" maxlength="3"
class="form-control length-3-input" />
但这是一个大问题:1.更改了Angular 2模型后触发了此限制,因此我将在模型中获得0值(但我需要1作为最小值).2.这只是更改输入值,而不更改Angular 2模型值.
But it is some big problem: 1. This limitation fired AFTER Angular 2 model changed, so I will get 0 value in model (but I need 1 as a min value). 2. This just change input value, but not Angular 2 model value.
那么,在更改Angular模型之前是否可以验证和阻止某些输入?
So, is it possible to validate and prevent some inputs before Angular model changed?
推荐答案
我应该使用自定义值访问器来实现此目的.这是一个示例:
I should use a custom value accessor to implement this. Here is a sample:
const CUSTOM_VALUE_ACCESSOR = new Provider(
NG_VALUE_ACCESSOR, {useExisting: forwardRef(() => MaxValueAccessor), multi: true});
@Directive ({
selector: 'input[max]',
host: { '(input)': 'doOnChange($event.target)' },
providers: [ CUSTOM_VALUE_ACCESSOR ]
})
export class MaxValueAccessor extends DefaultValueAccessor {
onChange = (_) => {};
onTouched = () => {};
writeValue(value:any):void {
if (value!=null) {
super.writeValue(value);
}
}
doOnChange(elt) {
var val = elt.value;
// check value here
elt.value = val;
this.onChange(val);
}
}
这样,您可以插入 ngModel
处理.
This way you can plug into the ngModel
handling.
有关更多详细信息,请参见此问题:
See this question for more details:
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