scroll-view 中的scrll-top值不生效

我是将scroll-view包装成了一个组件然后在,别的页面中调用,因为要实现一个回到顶部的功能,看了文档,试了好多次,scrll-top值都不生效,也百度谷歌了,

goTop: function(e) {  
this.scrollTop = this.old.scrollTop  
this.$nextTick(function() {  
this.scrollTop = 0  
});  
uni.showToast({  
icon:"none",  
title:"纵向滚动 scrollTop 值已被修改为 0"  
})  
}  
this.scollTop是要先等于this.old.scrollTop  
就被这一步给少了

上面的代码也试过了,意思就是说两次scrll-top值一样,所以不渲染.要先设成不一样的,在为0.试过无效.

附上我的代码.

<template>  
    <view>  
        <cu-custom bgColor="bg-gradual-theme" :isBack="true">  
            <block slot="backText">返回</block>  
            <block slot="content">{{ title }}</block>  
        </cu-custom>  
        <scroll-view scroll-y="true" class="scroll" :style="top" @scrolltolower="lower" :scroll-top="scrollTop" @scroll="scroll"><slot></slot></scroll-view>  
    </view>  
</template>  

<script>  
export default {  
    props: {  
        title: {  
            type: String,  
            default: '',  
            scrollTop: -1,  
            oldScrollTop: -1  
        }  
    },  
    data() {  
        return {  
            CustomBar: this.CustomBar  
        };  
    },  
    computed: {  
        top() {  
            return `top:${this.CustomBar}px`;  
        }  
    },  
    onLoad() {},  
    methods: {  
        lower: function(e) {  
            this.$emit('lower');  
        },  
        goTop() {  
            // this.scrollTop = this.oldScrollTop  
            this.$nextTick(()=>{  
                this.scrollTop = 0;  
                console.log(this.scrollTop)  
            });  
            // this.scrollTop = -1  
        },  
        scroll(e) {  
            this.scrollTop = e.detail.scrollTop;  
            // console.log(this.scrollTop)  
            // console.log(this.oldScrollTop)  
        }  
    }  
};  
</script>  

<style lang="scss" scoped>  
.scroll {  
    position: fixed;  
    bottom: 0;  
}  
</style>  

goTop函数在页面中通过this.$refs形式调用