iOS手机怎么下载文件，现在只能预览？

现在贴上点击下载按钮的方法，望指点，谢谢

exportMusicExcel() {    wx.showLoading({      title: '加载中'    })    let urlpath = app.globalData.urlPath;    let that = this;    let par = {      openId: this.data.openId,      cycle: this.data.cycleChange    }    api.exportMusicExcel(par).then(res => {      console.log(res);      let urlexcel = urlpath + res.data;            wx.downloadFile({        url: urlexcel,        success: function (res) {          const tempFilePath = res.tempFilePath;          // 保存文件          wx.saveFile({            tempFilePath,            success: function (res) {              const savedFilePath = res.savedFilePath;              // 打开文件              wx.openDocument({                filePath: savedFilePath,                success: function (res) {                  console.log('打开文档成功')                },              });            },            fail: function (err) {              console.log('保存失败：', err)            }          });        },        fail: function (err) {          console.log('下载失败：', err);        },      })    })  },