iOS supported placeholder property.

[Zhangguiguang]

No description provided.

[codecov]

Codecov Report

Merging #498 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #498   +/-   ##
=======================================
  Coverage   94.73%   94.73%           
=======================================
  Files           1        1           
  Lines          19       19           
=======================================
  Hits           18       18           
  Misses          1        1

---

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[codecov]

Codecov Report

Merging #498 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #498   +/-   ##
=======================================
  Coverage   94.73%   94.73%           
=======================================
  Files           1        1           
  Lines          19       19           
=======================================
  Hits           18       18           
  Misses          1        1

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7f080bf...62fd9c3. Read the comment docs.

[DylanVann]

Sorry for the delay. Thank you for the work on this. I’ve merged some work from #550, #741, and #498. If what’s on main now is missing anything important please open another PR. Thank you!